Forgot to initialize maximum position for mouse

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40929

src/video/gem/SDL_gemevents.c

@@ -302,6 +302,8 @@ static void do_mouse(_THIS, short mx, short my, short mb, short ks)
 
 	/* Retrieve window coords, and generate mouse events accordingly */
 	x2 = y2 = 0;
+	w2 = VDI_w;
+	h2 = VDI_h;
 	if ((!GEM_fullscreen) && (GEM_handle>=0)) {
 		wind_get (GEM_handle, WF_WORKXYWH, &x2, &y2, &w2, &h2);