Fixed dialog hanging on empty say text

Assets/Fungus/Dialog/Scripts/Dialog.cs

@@ -139,6 +139,10 @@ namespace Fungus.Script
 
 			if (glyphs.Count == 0)
 			{
+				if (onWritingComplete != null)
+				{
+					onWritingComplete();
+				}
 				yield break;
 			}