Only show the window if it's supposed to be shown.

src/video/cocoa/SDL_cocoawindow.m

@@ -613,9 +613,12 @@ SetWindowStyle(SDL_Window * window, unsigned int style)
         window->h = 0;
         [self windowDidResize:aNotification];
 
+        /* FIXME: Why does the window get hidden? */
+        if (window->flags & SDL_WINDOW_SHOWN) {
             Cocoa_ShowWindow(SDL_GetVideoDevice(), window);
         }
     }
+}
 
 -(NSApplicationPresentationOptions)window:(NSWindow *)window willUseFullScreenPresentationOptions:(NSApplicationPresentationOptions)proposedOptions
 {