Solve special case of previous fix

The case when the lambda function is not declared within a class.

src/Peachpie.CodeAnalysis/CodeGen/CodeGenerator.cs

@@ -296,7 +296,10 @@ internal void BlockGenerated(BoundBlock block)
         /// <summary>
         /// Type of the caller context (the class declaring current method) or null.
         /// </summary>
-        public TypeSymbol CallerType => (_routine is SourceMethodSymbol || _routine is SourceLambdaSymbol) ? _routine.ContainingType : null;
+        public TypeSymbol CallerType => 
+            (_routine is SourceMethodSymbol) ? _routine.ContainingType :
+            (_routine is SourceLambdaSymbol) ? _routine.ContainingType as SourceTypeSymbol :
+            null;
 
         public SourceFileSymbol ContainingFile => _containingFile;
         SourceFileSymbol _containingFile;