Hold a reference on the Window while emitting events from vcl backends.

Change-Id: I4673dc03c214ca8f5c227a444e182a45f6199b9b

vcl/source/window/winproc.cxx

@@ -2377,11 +2377,14 @@ static void ImplHandleSalQueryCharPosition( vcl::Window *pWindow,
     }
 }
 
-bool ImplWindowFrameProc( vcl::Window* pWindow, SalFrame* /*pFrame*/,
+bool ImplWindowFrameProc( vcl::Window* _pWindow, SalFrame* /*pFrame*/,
                           sal_uInt16 nEvent, const void* pEvent )
 {
     DBG_TESTSOLARMUTEX();
 
+    // Ensure the window survives during this method.
+    VclPtr<vcl::Window> pWindow( _pWindow );
+
     bool nRet = false;
 
     // #119709# for some unknown reason it is possible to receive events (in this case key events)