Delete window surfaces before breaking the connection to the X server

Otherwise, destroying the OpenGL context would crash.

src/C4FullScreen.cpp

@@ -413,6 +413,13 @@ void C4FullScreen::Close()
 		Application.Quit();
 	}
 
+void C4FullScreen::Clear()
+	{
+	if (pSurface) delete pSurface;
+	pSurface = 0;
+	CStdWindow::Clear();
+	}
+
 void C4FullScreen::Execute()
 	{
 	// Execute menu

src/C4FullScreen.h

@@ -46,6 +46,7 @@ class C4FullScreen: public CStdWindow
 		bool MenuKeyControl(BYTE byCom); // direct keyboard callback
 		// User requests close
 		virtual void Close();
+		virtual void Clear();
 		virtual void CharIn(const char * c);
 #ifdef USE_X11
 		virtual void HandleMessage (XEvent &e);

src/editor/C4Console.cpp

@@ -1190,6 +1190,8 @@ void C4Console::Clear()
 	ClearViewportMenu();
 	ClearPlayerMenu();
 	ClearNetMenu();
+	if(pSurface) delete pSurface;
+	pSurface = 0;
 #ifndef _WIN32
 	Application.Quit();
 #endif