ve.ui.MWMediaResultWidget: Use .on() instead of .error()

> JQMIGRATE: jQuery.fn.error() is deprecated.

While at it, also avoid using the overloaded .load(). It has
quite a few different signatures (one of them is to load $.ajax
by url and replace the contents of the element, completely
unrelated), and calling .on() directly is quicker as well.

Change-Id: I139b0c603577b5a0102d2ff679bd86b792830e3e
Merge "ve.ui.MWMediaResultWidget: Use .on() instead of .error()"