Fix segfault in C# layer handling using declarations

Segfault was actually avoided in previous commit ab23cb29.
This commit makes handling more robust in the event of
using %ignore just on the derived method, not tested as it is not
what one should do with directors, and possibly other cases.

Go still segfaults with the new testcase director_using_member_scopes.i.

Issue #1441.

Examples/test-suite/common.mk

@@ -218,6 +218,7 @@ CPP_TEST_CASES += \
 	director_thread \
 	director_unroll \
 	director_using \
+	director_using_member_scopes \
 	director_void \
 	director_wombat \
 	disown \

Examples/test-suite/director_using_member_scopes.i

@@ -0,0 +1,32 @@
+%module(directors="1") director_using_member_scopes
+
+// Similar to using_member_scopes but for directors
+
+#if !defined(SWIGGO)
+
+%feature("director");
+// Python,Java,C# no diffs in generated code when adding in nodirector. Go not happy even without %nodirector.
+// Fully qualifying parameter types in a method declared after the using declaration caused
+// a method being incorrectly added by the using declaration even though the declaration already existed
+
+// Github issue #1441 - segfault in Go and C#
+
+%inline %{
+namespace OgreBites
+{
+    struct NativeWindowType {};
+    class ApplicationContextBase {
+    public:
+        virtual ~ApplicationContextBase() {}
+        virtual void setWindowGrab(NativeWindowType* win, bool grab = true) {}
+        void setWindowGrab(bool grab = true) {}
+    };
+    class ApplicationContextSDL : public ApplicationContextBase {
+    public:
+        using ApplicationContextBase::setWindowGrab;
+        void setWindowGrab(NativeWindowType* win, bool grab) {} // This should not be added again as it exists in base class
+    };
+}
+%}
+
+#endif

Source/Modules/csharp.cxx

@@ -2553,8 +2553,8 @@ public:
 	Replaceall(imcall, "$imfuncname", intermediary_function_name);
 	String *excode = NewString("");
 	Node *directorNode = Getattr(n, "directorNode");
-	if (directorNode) {
+	UpcallData *udata = directorNode ? Getattr(directorNode, "upcalldata") : 0;
-	  UpcallData *udata = Getattr(directorNode, "upcalldata");
+	if (udata) {
 	  String *methid = Getattr(udata, "class_methodidx");
 
 	  if (!Cmp(return_type, "void"))