winemac: Don't complain that WM_MACDRV_ACTIVATE_ON_FOLLOWING_FOCUS is unrecognized.

dlls/winemac.drv/window.c

@@ -1239,7 +1239,7 @@ LRESULT CDECL macdrv_WindowMessage(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp)
         activate_on_focus_time = GetTickCount();
         if (!activate_on_focus_time) activate_on_focus_time = 1;
         TRACE("WM_MACDRV_ACTIVATE_ON_FOLLOWING_FOCUS time %u\n", activate_on_focus_time);
-        break;
+        return 0;
     }
 
     FIXME("unrecognized window msg %x hwnd %p wp %lx lp %lx\n", msg, hwnd, wp, lp);