TextMeshProについて。開始するとぼやける。

Question

https://unitech.hatenablog.com/entry/2017/11/18/183658
こちらのサイトを参考にして、TMPのテキストをアーチ状に曲げる方法を実装しようとしています。

TextMeshPro-Text(UI)にArched Textをアタッチすると、シーンとゲーム画面でテキストがちゃんと曲がっているように表示されます。
しかし、ゲームを開始時と終了時に、以下のエラーが表示され、テキストがぼやけて表示されてしまいます。

NullReferenceException: Object reference not set to an instance of an object
ArchedText.UpdateCurveMesh () (at Assets/Scripts/ArchedText.cs:45)
ArchedText.OnValidate () (at Assets/Scripts/ArchedText.cs:168)

参照を持たない参照変数にアクセスしたときに出るエラーなのですが、該当エラー箇所を見ても目立って間違っている部分があるとは分かりませんでした。もし、なにか知見をお持ちの方がいらっしゃったらお願い致します。

＜該当エラー箇所＞

textComponent.ForceMeshUpdate();

UpdateCurveMesh ();

＜Arched Text全文＞

using UnityEngine;
using TMPro;
using System.Collections;

#if UNITY_EDITOR
using UnityEditor;
#endif

[ExecuteInEditMode]
public class ArchedText : MonoBehaviour 
{
	public enum TextVAlignment
	{
		Base,
		Top,
		Bottom,
	}

	[SerializeField]
	private TextVAlignment vAlignment;
	[SerializeField]
	private TextAlignment hAlignment;
	[SerializeField]
	private AnimationCurve vertexCurve = new AnimationCurve (new Keyframe (0, 0), new Keyframe (0.5f, 0.25f), new Keyframe (1, 0f));

	private TMP_Text textComponent;

	void Awake ()
	{
		textComponent = gameObject.GetComponent<TMP_Text> ();
	}

	void Update ()
	{
		if (!textComponent.havePropertiesChanged) 
		{
			return;
		}

		UpdateCurveMesh ();
	}

	void UpdateCurveMesh ()
	{
		textComponent.ForceMeshUpdate();

		TMP_TextInfo textInfo = textComponent.textInfo;
		int characterCount = textInfo.characterCount;

		if (characterCount == 0)
			return;

		Vector3 baseline = new Vector3();
		Vector3 prevAngleDirection = new Vector3();
		Vector3 prevOffsetToMidBaseline = new Vector3();
		Vector3[] vertices;
		Matrix4x4 matrix;
		float defaultBaseLine = 0;
		float maxBaseLine = float.MinValue;
		float minBaseLine = float.MaxValue;
		bool isFirst = true;

		for (int i = 0; i < characterCount; i++) 
		{
			if (!textInfo.characterInfo [i].isVisible)
				continue;

			int vertexIndex = textInfo.characterInfo [i].vertexIndex;

			int materialIndex = textInfo.characterInfo [i].materialReferenceIndex;
			vertices = textInfo.meshInfo [materialIndex].vertices;

			//文字の真ん中の点と文字の基準となるベースラインの高さを取得
			Vector3 offsetToMidBaseline = new Vector2 ((vertices [vertexIndex + 0].x + vertices [vertexIndex + 2].x) / 2, textInfo.characterInfo [i].baseLine);

			//文字の中央の下が原点となるように頂点を移動（これから回転と移動をさせるため）
			vertices [vertexIndex + 0] += -offsetToMidBaseline;
			vertices [vertexIndex + 1] += -offsetToMidBaseline;
			vertices [vertexIndex + 2] += -offsetToMidBaseline;
			vertices [vertexIndex + 3] += -offsetToMidBaseline;

			//曲線の傾き(agnle)の計算
			float x0 = (float)(i + 1) / (characterCount + 1);
			float x1 = x0 + 0.0001f;
			float y0 = vertexCurve.Evaluate (x0);
			float y1 = vertexCurve.Evaluate (x1);
			Vector3 horizontal = new Vector3 (1, 0, 0);
			Vector3 tangent = new Vector3 (0.0001f, (y1 - y0));
			Vector3 angleDirection = tangent.normalized;
			float angle = Mathf.Acos (Vector3.Dot (horizontal, angleDirection)) * Mathf.Rad2Deg;
			Vector3 cross = Vector3.Cross (horizontal, tangent);
			angle = cross.z > 0 ? angle : 360 - angle;

			//angle回転させた頂点位置の計算
			matrix = Matrix4x4.Rotate (Quaternion.Euler (0, 0, angle));
			vertices [vertexIndex + 0] = matrix.MultiplyPoint3x4 (vertices [vertexIndex + 0]);
			vertices [vertexIndex + 1] = matrix.MultiplyPoint3x4 (vertices [vertexIndex + 1]);
			vertices [vertexIndex + 2] = matrix.MultiplyPoint3x4 (vertices [vertexIndex + 2]);
			vertices [vertexIndex + 3] = matrix.MultiplyPoint3x4 (vertices [vertexIndex + 3]);

			//文字間の計算
			float characterSpace;
			if (isFirst) 
			{
				baseline = offsetToMidBaseline;
				defaultBaseLine = baseline.y;
				characterSpace = 0;
				isFirst = false;
			} 
			else 
			{
				characterSpace = (offsetToMidBaseline - prevOffsetToMidBaseline).magnitude;
			}
			prevOffsetToMidBaseline = offsetToMidBaseline;

			//文字位置を計算して移動
			baseline = baseline + (angleDirection + prevAngleDirection).normalized * characterSpace;
			vertices [vertexIndex + 0] += baseline;
			vertices [vertexIndex + 1] += baseline;
			vertices [vertexIndex + 2] += baseline;
			vertices [vertexIndex + 3] += baseline;

			prevAngleDirection = angleDirection;

			minBaseLine = Mathf.Min (minBaseLine, baseline.y);
			maxBaseLine = Mathf.Max (maxBaseLine, baseline.y);
		}

		//揃えの計算
		if (hAlignment != TextAlignment.Left || vAlignment != TextVAlignment.Base) 
		{
			float hOffset = 0;
			if (hAlignment == TextAlignment.Center)
				hOffset = (prevOffsetToMidBaseline.x - baseline.x) * 0.5f;
			else if (hAlignment == TextAlignment.Right)
				hOffset = (prevOffsetToMidBaseline.x - baseline.x);

			float vOffset = 0;
			if (vAlignment == TextVAlignment.Bottom)
				vOffset = defaultBaseLine - minBaseLine;
			else if (vAlignment == TextVAlignment.Top)
				vOffset = defaultBaseLine - maxBaseLine;
			
			Vector3 alignOffset = new Vector3 (hOffset, vOffset, 0);

			for (int i = 0; i < characterCount; i++) 
			{
				if (!textInfo.characterInfo [i].isVisible)
					continue;

				int vertexIndex = textInfo.characterInfo [i].vertexIndex;
				int materialIndex = textInfo.characterInfo [i].materialReferenceIndex;
				vertices = textInfo.meshInfo [materialIndex].vertices;

				vertices [vertexIndex + 0] += alignOffset;
				vertices [vertexIndex + 1] += alignOffset;
				vertices [vertexIndex + 2] += alignOffset;
				vertices [vertexIndex + 3] += alignOffset;
			}
		}

		textComponent.UpdateVertexData ();
	}
		
#if UNITY_EDITOR
	protected virtual void OnValidate()
	{
		UpdateCurveMesh ();
	}

	void OnEnable()
	{
		UpdateCurveMesh ();
	}

	void OnDisable()
	{
		textComponent.ForceMeshUpdate();
	}
#endif
}