Reset codegen target after parsing nested function

Parsing a function expression inside another function failed to reset
the code generator target to the containing function, so all following
bytecode would still be appended to the nested function, leaving the
container broken.

src/script/C4AulParse.cpp

@@ -2217,6 +2217,7 @@ C4Value C4AulParse::Parse_ConstExpression(C4PropListStatic * parent, C4String *
 			Shift();
 			Parse_FuncBody();
 			Fn = prev_Fn;
+			codegen.Fn = Fn;
 		}
 		else
 		{