winemac: Make show_window() and hide_window() tolerate being called when there's no Cocoa window.

dlls/winemac.drv/window.c

@@ -731,6 +731,8 @@ static struct macdrv_win_data *macdrv_create_win_data(HWND hwnd, const RECT *win
  */
 static void show_window(struct macdrv_win_data *data)
 {
+    if (data->cocoa_window)
+    {
         HWND prev = NULL;
         HWND next = NULL;
         macdrv_window prev_window = NULL;
@@ -765,6 +767,7 @@ static void show_window(struct macdrv_win_data *data)
             macdrv_SetFocus(hwndFocus);
         if (activate)
             activate_on_focus_time = 0;
+    }
 }
 
 
@@ -775,6 +778,7 @@ static void hide_window(struct macdrv_win_data *data)
 {
     TRACE("win %p/%p\n", data->hwnd, data->cocoa_window);
 
+    if (data->cocoa_window)
         macdrv_hide_cocoa_window(data->cocoa_window);
     data->on_screen = FALSE;
 }