Qt4 - revert the revertion :D

Jokes besides, if ~MainInterface() is called, then p_mi is destroyed, and p_sys->p_mi too. I just hope I am not wrong :D

modules/gui/qt4/main_interface.cpp

@@ -352,6 +352,7 @@ MainInterface::~MainInterface()
     p_intf->pf_request_window = NULL;
     p_intf->pf_release_window = NULL;
     p_intf->pf_control_window = NULL;
+    p_intf->p_sys->p_mi = NULL;
 }
 
 /*****************************

modules/gui/qt4/qt4.cpp

@@ -320,7 +320,6 @@ static void Init( intf_thread_t *p_intf )
     /* And quit */
     MainInputManager::killInstance();
     DialogsProvider::killInstance();
-    delete p_intf->p_sys->p_mi;
     delete app;
 }