Try to improve load error message
Try to improve load error message

Necessary until refreshing assets works better...

Closes #112.

flarum/english,FlarumChina/flarum-ext-simplified-chinese-pro,ogioncz/flarum-ext-czech,FlarumChina/flarum-ext-simplified-chinese-pro,flarum/flarum-ext-english,ogioncz/flarum-ext-czech