TDCU: make sure that copies of display-class variables are validated as well.

ICSharpCode.Decompiler/IL/Transforms/TransformDisplayClassUsage.cs

@@ -204,7 +204,6 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 
 		bool ValidateDisplayClassUses(ILVariable v, DisplayClass displayClass)
 		{
-			Debug.Assert(v == displayClass.Variable);
 			foreach (var ldloc in v.LoadInstructions)
 			{
 				if (!ValidateUse(displayClass, ldloc))
@@ -239,7 +238,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						return false;
 					case StLoc stloc when stloc.Variable.IsSingleDefinition && stloc.Value == use:
 						displayClassCopyMap[stloc.Variable] = v;
-						return true;
+						return ValidateDisplayClassUses(stloc.Variable, displayClass);
 					default:
 						return false;
 				}