ruby version変更によってherokuにデプロイできません

herokuで表示させていたアプリが、rubyのversionを変更した別アプリを作成したことによって表示できなくなってしまいました。そこでheroku logsで確認すると下記のエラーが表示されます。ログが長いので詳細を書きたかったのですがかけず。

2018-01-05T10:05:30.344925+00:00 heroku[web.1]: State changed from up to down
2018-01-05T10:05:31.290774+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2018-01-05T10:05:31.462600+00:00 app[web.1]: /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/webrick/server.rb:177:in `block in start'
2018-01-05T10:05:31.462598+00:00 app[web.1]: /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/webrick/server.rb:177:in `select'
2018-01-05T10:05:31.462601+00:00 app[web.1]: /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/webrick/server.rb:33:in `start'
2018-01-05T10:05:31.462602+00:00 app[web.1]: /app/vendor/ruby-2.3.0/lib/ruby/2.3.0/webrick/server.rb:164:in `start'
2018-01-05T10:05:31.462602+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/rack-1.6.8/lib/rack/handler/webrick.rb:34:in `run'
2018-01-05T10:05:31.462603+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/rack-1.6.8/lib/rack/server.rb:287:in `start'
2018-01-05T10:05:31.462582+00:00 app[web.1]: [2018-01-05 10:05:31] FATAL SignalException: SIGTERM
2018-01-05T10:05:31.462604+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/railties-4.2.6/lib/rails/commands/server.rb:80:in `start'
2018-01-05T10:05:31.462605+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/railties-4.2.6/lib/rails/commands/commands_tasks.rb:80:in `block in server'
2018-01-05T10:05:31.462607+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/railties-4.2.6/lib/rails/commands/commands_tasks.rb:75:in `server'
2018-01-05T10:05:31.462606+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/railties-4.2.6/lib/rails/commands/commands_tasks.rb:75:in `tap'
2018-01-05T10:05:31.462608+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/railties-4.2.6/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
2018-01-05T10:05:31.462608+00:00 app[web.1]: /app/vendor/bundle/ruby/2.3.0/gems/railties-4.2.6/lib/rails/commands.rb:17:in `<top (required)>'
2018-01-05T10:05:31.462610+00:00 app[web.1]: bin/rails:9:in `require'
2018-01-05T10:05:31.464799+00:00 app[web.1]: [2018-01-05 10:05:31] INFO  going to shutdown ...
2018-01-05T10:05:31.462610+00:00 app[web.1]: bin/rails:9:in `<main>'
2018-01-05T10:05:31.464924+00:00 app[web.1]: [2018-01-05 10:05:31] INFO  WEBrick::HTTPServer#start done.
2018-01-05T10:05:31.465065+00:00 app[web.1]: Exiting
2018-01-05T10:05:32.856014+00:00 heroku[web.1]: Process exited with status 143
2018-01-05T13:40:40.239111+00:00 heroku[web.1]: State changed from down to starting
2018-01-05T13:40:46.768542+00:00 heroku[web.1]: Starting process with command `bin/rails server -p 6179 -e production`
2018-01-05T13:40:57.479464+00:00 app[web.1]: [2018-01-05 13:40:57] INFO  WEBrick 1.3.1
2018-01-05T13:40:57.479516+00:00 app[web.1]: [2018-01-05 13:40:57] INFO  ruby 2.3.0 (2015-12-25) [x86_64-linux]
2018-01-05T13:40:57.479964+00:00 app[web.1]: [2018-01-05 13:40:57] INFO  WEBrick::HTTPServer#start: pid=4 port=6179
2018-01-05T13:40:57.814314+00:00 heroku[web.1]: State changed from starting to up
2018-01-05T13:40:59.531955+00:00 app[web.1]: => Booting WEBrick
2018-01-05T13:40:59.531967+00:00 app[web.1]: => Rails 4.2.6 application starting in production on http://0.0.0.0:6179
2018-01-05T13:40:59.531968+00:00 app[web.1]: => Run `rails server -h` for more startup options
2018-01-05T13:40:59.531968+00:00 app[web.1]: => Ctrl-C to shutdown server
2018-01-05T13:40:59.531969+00:00 app[web.1]: Started GET "/" for 118.240.175.28 at 2018-01-05 13:40:59 +0000
2018-01-05T13:40:59.658473+00:00 app[web.1]: Processing by PagesController#index as HTML
2018-01-05T13:40:59.685484+00:00 app[web.1]:   Rendered partial/_navbar.html.erb (7.5ms)
2018-01-05T13:41:00.593858+00:00 app[web.1]:   User Load (2.6ms)  SELECT "users".* FROM "users"
2018-01-05T13:41:00.795241+00:00 app[web.1]:   Listing Load (2.1ms)  SELECT "listings".* FROM "listings" WHERE "listings"."user_id" = $1  [["user_id", 4]]
2018-01-05T13:41:00.888763+00:00 app[web.1]:   Photo Load (3.2ms)  SELECT "photos".* FROM "photos" WHERE "photos"."listing_id" = $1  [["listing_id", 25]]
2018-01-05T13:41:00.892835+00:00 app[web.1]:   Rendered pages/index.html.erb within layouts/application (1217.5ms)
2018-01-05T13:41:00.898406+00:00 app[web.1]: Completed 500 Internal Server Error in 1239ms (ActiveRecord: 32.6ms)
2018-01-05T13:41:00.907925+00:00 app[web.1]:
2018-01-05T13:41:00.907929+00:00 app[web.1]: ActionView::Template::Error (undefined method `image' for nil:NilClass):
2018-01-05T13:41:00.907932+00:00 app[web.1]:     89:           <% if !user.listings.blank?%>
2018-01-05T13:41:00.907933+00:00 app[web.1]:     90:             <div class="col-md-4 col-sm-6 portfolio-item row-space-2">
2018-01-05T13:41:00.907934+00:00 app[web.1]:     91:               <%= link_to listing_path(user.listings[0]) do %>
2018-01-05T13:41:00.907935+00:00 app[web.1]:     92:                 <%= image_tag user.listings[0].photos[0].image.url(:medium) %>
2018-01-05T13:41:00.907938+00:00 app[web.1]:     95:                 <%= image_tag user.image,class:"img-circle profile-1"%>
2018-01-05T13:41:00.907972+00:00 app[web.1]:   app/views/pages/index.html.erb:88:in `_app_views_pages_index_html_erb__2695958356563593208_70064641064040'
2018-01-05T13:41:00.907936+00:00 app[web.1]:     93:               <% end %>
2018-01-05T13:41:00.907967+00:00 app[web.1]:   app/views/pages/index.html.erb:92:in `block (2 levels) in _app_views_pages_index_html_erb__2695958356563593208_70064641064040'
2018-01-05T13:41:00.907937+00:00 app[web.1]:     94:               <div class="portfolio-caption">
2018-01-05T13:41:00.907969+00:00 app[web.1]:   app/views/pages/index.html.erb:91:in `block in _app_views_pages_index_html_erb__2695958356563593208_70064641064040'