Emscripten: don't zero the display mode before adding it

src/video/emscripten/SDL_emscriptenvideo.c

@@ -156,7 +156,6 @@ Emscripten_VideoInit(_THIS)
         return -1;
     }
 
-    SDL_zero(mode);
     SDL_AddDisplayMode(&_this->displays[0], &mode);
 
     Emscripten_InitMouse();