cocoa_common: improve conditional dock hiding from 3259e4a7a

Make the conditional hiding logic introduced in commit 3259e4a7a2a938
("cocoa_common: make fullscreen menubar/dock hiding conditional") work
when mplayer is started with the `fs` and `xineramascreen` options.

libvo/cocoa_common.m

@@ -666,8 +666,9 @@ void create_menu()
     if (vo_fs) {
         [s->window makeKeyAndOrderFront:s->window];
         [s->window setLevel:s->fullscreen_window_level];
-        [NSApp setPresentationOptions:NSApplicationPresentationHideDock|
-                                      NSApplicationPresentationHideMenuBar];
+        if (current_screen_has_dock_or_menubar())
+            [NSApp setPresentationOptions:NSApplicationPresentationHideDock|
+                                          NSApplicationPresentationHideMenuBar];
     }
 }