Report emoji texture image load issue.

Author: Yuncong Zhang

Runtime/ui/painting/canvas_impl.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Net;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.material;
 using UnityEngine;
@@ -770,6 +771,7 @@ void _drawTextBlob(TextBlob textBlob, Offset offset, Paint paint) {
                 }
                 else {
                     Paint paintWithWhite = new Paint(p) {color = Colors.white};
+                    if (EmojiUtils.image == null) return;
                     layer.draws.Add(CanvasShader.tex(layer, paintWithWhite, mesh.resolveMesh(), EmojiUtils.image));
                 }
             };

Runtime/ui/txt/emoji.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Unity.UIWidgets.foundation;
 using UnityEngine;
 
 namespace Unity.UIWidgets.ui {
@@ -14,8 +15,9 @@ public static Image image {
                             Resources.Load<Texture2D>("Emoji")
                         );
                     }
-                    catch (Exception) {
+                    catch (Exception e) {
                         _image = null;
+                        Debug.LogError(e.StackTrace);
                     }
                 }