file_advanced clone index off by 1

[andrewfrankel]

This is similar to the issue found at #875 but when using file_advanced fields. FWIW the placeholder disabled input field upon cloning appears to have the correct index, it only becomes a problem once you add the file and the hidden input containing the file id has the wrong index.

Duplicate values:

<input disabled="" class="rwmb-file_advanced" name="secondary_logos[0][logo_jpg][]" type="hidden" value="899,897">

[andywall9]

Just to add to this issue as this seems to be basically the same thing, I'm having the same problem with cloning all field groups. Whenever I add a new one and save, it just overwrites the last one, no matter how many there were previously.

[funkatron82]

Is this still an issue?

[andrewfrankel]

@funkedgeek haven't had a chance to re-test with the latest code.