firebaseとdjangoを使ったサービスでupdate機能を実装したい

Question

ブラウザ上でsubmitボタンを押した後にupdate機能を発火させようとすると、float() argument must be a string or a number, not 'NoneType'というエラーがupdate関数のi = float(time)という文で出力されます。この原因はどうしてなのでしょうか？
index.py

from django.shortcuts import render
import pyrebase
from django.contrib import auth
import time
from datetime import datetime, timezone
import pytz
from django.shortcuts import redirect

config = {
    "apiKey": "AIzaSyDQpcXwK5Ozd8clDuFSYBLyIqButglyRmM",
    "authDomain": "moaiproject-83e9a.firebaseapp.com",
    "databaseURL": "https://moaiproject-83e9a.firebaseio.com",
    "projectId": "moaiproject-83e9a",
    "storageBucket": "moaiproject-83e9a.appspot.com",
    "messagingSenderId": "832006927247",
    "appId": "1:832006927247:web:044b91eef444fc6c"
}
firebase = pyrebase.initialize_app(config)

authe = firebase.auth()
database=firebase.database()
def signIn(request):

    return render(request, "signIn.html")

def list(request):
    email=request.POST.get('email')
    password = request.POST.get("password")
    try:
        user = authe.sign_in_with_email_and_password(email,password)
    except:
        errorMessage="invalid credentials"
        return render(request,"signIn.html",{"errorMessage":errorMessage})
    session_id=user['idToken']
    request.session['uid']=str(session_id)
    import datetime
    idtoken = request.session['uid']
    a = authe.get_account_info(idtoken)
    a = a['users']
    a = a[0]
    a = a['localId']

    timestamps = database.child('users').child(a).child('reports').shallow().get().val()
    lis_time=[]
    if timestamps:
        for i in timestamps:

            lis_time.append(i)

        lis_time.sort(reverse=True)

        work = []

        for i in lis_time:

            wor=database.child('users').child(a).child('reports').child(i).child('work').get().val()
            work.append(wor)

        date=[]
        for i in lis_time:
            i = float(i)
            dat = datetime.datetime.fromtimestamp(i).strftime('%H:%M %d-%m-%Y')
            date.append(dat)


        comb_lis = zip(lis_time,date,work)
        name = database.child('users').child(a).child('details').child('name').get().val()
        return render(request, "welcome.html",{'comb_lis':comb_lis,"e":email})
    else:
        return render(request, "welcome.html",{"e":email})



def logout(request):
    auth.logout(request)
    return redirect('/')


def signUp(request):

    return render(request,"signup.html")
def postsignup(request):

    name=request.POST.get('name')
    email=request.POST.get('email')
    password=request.POST.get('password')
    try:
        user=authe.create_user_with_email_and_password(email,password)
    except:
        errorMessag="Unable to create account try again"
        return render(request,"signup.html",{"errorMessage":errorMessag})

    uid = user['localId']

    data={"name":name,"status":"1"}

    database.child("users").child(uid).child("details").set(data)
    return redirect('/')

def create(request):

    return render(request,'create.html')


def post_create(request):



    tz= pytz.timezone('Asia/Tokyo')
    time_now= datetime.now(timezone.utc).astimezone(tz)
    millis = int(time.mktime(time_now.timetuple()))
    print("mili"+str(millis))
    work = request.POST.get('work')
    progress =request.POST.get('progress')
    url = request.POST.get('url')
    idtoken= request.session['uid']
    a = authe.get_account_info(idtoken)
    a = a['users']
    a = a[0]
    a = a['localId']
    data = {
        "work":work,
        'progress':progress,
        'url':url
    }
    database.child('users').child(a).child('reports').child(millis).set(data)
    name = database.child('users').child(a).child('details').child('name').get().val()
    
    
    timestamps = database.child('users').child(a).child('reports').shallow().get().val()
    lis_time=[]
    if timestamps:
        for i in timestamps:

            lis_time.append(i)

        lis_time.sort(reverse=True)

        work = []

        for i in lis_time:

            wor=database.child('users').child(a).child('reports').child(i).child('work').get().val()
            work.append(wor)

        date=[]
        for i in lis_time:
            i = float(i)
            dat = datetime.fromtimestamp(i).strftime('%H:%M %d-%m-%Y')
            date.append(dat)


        comb_lis = zip(lis_time,date,work)
        name = database.child('users').child(a).child('details').child('name').get().val()
        return render(request, "welcome.html",{'comb_lis':comb_lis,"e":name})
    else:
        return render(request, "welcome.html",{"e":email})

def post_check(request):

    import datetime

    time = request.GET.get('z')

    idtoken = request.session['uid']
    a = authe.get_account_info(idtoken)
    a = a['users']
    a = a[0]
    a = a['localId']

    work =database.child('users').child(a).child('reports').child(time).child('work').get().val()
    progress =database.child('users').child(a).child('reports').child(time).child('progress').get().val()
    img_url = database.child('users').child(a).child('reports').child(time).child('url').get().val()
    i = float(time)
    dat = datetime.datetime.fromtimestamp(i).strftime('%H:%M %d-%m-%Y')
    name = database.child('users').child(a).child('details').child('name').get().val()

    return render(request,'post_check.html',{'w':work,'p':progress,'d':dat,'e':name,'i':img_url})

def delete(request):

    time = request.GET.get("z")
    
    idtoken = request.session['uid']
    a = authe.get_account_info(idtoken)
    a = a['users']
    a = a[0]
    a = a['localId']
    
    database.child('users').child(a).child('reports').child(time).remove()
    
        
    timestamps = database.child('users').child(a).child('reports').shallow().get().val()
    lis_time=[]
    if timestamps:
        for i in timestamps:

            lis_time.append(i)

        lis_time.sort(reverse=True)

        work = []

        for i in lis_time:

            wor=database.child('users').child(a).child('reports').child(i).child('work').get().val()
            work.append(wor)

        date=[]
        for i in lis_time:
            i = float(i)
            dat = datetime.fromtimestamp(i).strftime('%H:%M %d-%m-%Y')
            date.append(dat)


        comb_lis = zip(lis_time,date,work)
        name = database.child('users').child(a).child('details').child('name').get().val()
        return render(request, "welcome.html",{'comb_lis':comb_lis,"e":name})
    else:
        return render(request, "welcome.html",{"e":email})
    
def update(request):

    import datetime

    time = request.GET.get('z')

    idtoken = request.session['uid']
    a = authe.get_account_info(idtoken)
    a = a['users']
    a = a[0]
    a = a['localId']

    work =database.child('users').child(a).child('reports').child(time).child('work').get().val()
    progress =database.child('users').child(a).child('reports').child(time).child('progress').get().val()
    img_url = database.child('users').child(a).child('reports').child(time).child('url').get().val()
    i = float(time)
    dat = datetime.datetime.fromtimestamp(i).strftime('%H:%M %d-%m-%Y')
    name = database.child('users').child(a).child('details').child('name').get().val()

    return render(request,'update.html',{'w':work,'p':progress,'d':dat,'e':name,'i':img_url})

def post_update(request):
    

    time = request.GET.get('z')
    tz= pytz.timezone('Asia/Tokyo')
    time_now= datetime.now(timezone.utc).astimezone(tz)
    # millis = int(time.mktime(time_now.timetuple()))
    # print("mili"+str(millis))
    work = request.POST.get('work')
    progress =request.POST.get('progress')
    url = request.POST.get('url')
    idtoken= request.session['uid']
    a = authe.get_account_info(idtoken)
    a = a['users']
    a = a[0]
    a = a['localId']
    data = {
        "work":work,
        'progress':progress,
        'url':url
    }
    database.child('users').child(a).child('reports').child(time).update(data)
    name = database.child('users').child(a).child('details').child('name').get().val()
    
    
    timestamps = database.child('users').child(a).child('reports').shallow().get().val()
    lis_time=[]
    if timestamps:
        for i in timestamps:

            lis_time.append(i)

        lis_time.sort(reverse=True)

        work = []

        for i in lis_time:

            wor=database.child('users').child(a).child('reports').child(i).child('work').get().val()
            work.append(wor)

        date=[]
        for i in lis_time:
            i = float(i)
            dat = datetime.fromtimestamp(i).strftime('%H:%M %d-%m-%Y')
            date.append(dat)


        comb_lis = zip(lis_time,date,work)
        name = database.child('users').child(a).child('details').child('name').get().val()
        return render(request, "welcome.html",{'comb_lis':comb_lis,"e":name})
    else:
        return render(request, "welcome.html",{"e":email})