Fix error on text frame update if texture not found.

Assets/Cryville/Crtr/Components/SpriteText.cs

@@ -81,6 +81,7 @@ namespace Cryville.Crtr.Components {
 			materials = new Material[m_frames.Count];
 			int i = 0;
 			foreach (var f in m_frames) {
+				if (SpriteInfo.IsNullOrEmpty(f.Value)) continue;
 				if (frameHeight == 0) frameHeight = f.Value.Rect.height;
 				else if (frameHeight != f.Value.Rect.height) throw new Exception("Inconsistent frame height for text component");
 				var tex = f.Value.Frame.Texture;