Wikimedia Bugzilla is closed!

TypeError: $file.attr(...) is undefined
	
data.fileType = $file.attr( 'alt' ).split( '.' ).pop();

The source of the issue is this line:

$file = $( '#file' ).find( 'img' );

Which assumes the presence of an image and passes the empty jQuery object further along.

I think this might be a race condition to a degree, as the image might be part of the DOM returned by the server, but TMH hijacks it as soon as it can.