X11: only send mouse button up events if not a mousewheel "button"

(Brackets in the wrong place, my bad!)

src/video/x11/SDL_x11events.c

@@ -1029,8 +1029,8 @@ X11_DispatchEvent(_THIS)
                     /* see explanation at case ButtonPress */
                     button -= (8-SDL_BUTTON_X1);
                 }
+                SDL_SendMouseButton(data->window, 0, SDL_RELEASED, button);
             }
-            SDL_SendMouseButton(data->window, 0, SDL_RELEASED, button);
         }
         break;