tdf#117034 right click crash

Change-Id: I91aa9f24904948987f31c9df5211c694f943188e
Reviewed-on: https://gerrit.libreoffice.org/52976Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/unx/gtk3/gtk3gtkinst.cxx

@@ -1573,7 +1573,7 @@ public:
             nTime = GtkSalFrame::GetLastInputEventTime();
         }
 
-        gtk_menu_popup(GTK_MENU(pWidget), nullptr, nullptr, nullptr, nullptr, nButton, nTime);
+        gtk_menu_popup(m_pMenu, nullptr, nullptr, nullptr, nullptr, nButton, nTime);
 #endif
 
         if (g_main_loop_is_running(pLoop))