Update list.php

Fabrik adds '&rowid=...' to custom links if the link string doesn't contain the "{rowid}" placeholder. However, it is also the case that Fabrik shouldn't add '&rowid=...' to custom links if the link sets the value of rowid to something besides '{rowid}' in the query string. So, for example, a custom edit link like "?option=com_fabrik&view=form&formid=2&rowid=123" gets turned into "?option=com_fabrik&view=form&formid=2&rowid=123&rowid=whatever", which isn't what we want.

This change adds a check to see if 'rowid=' is already present in the custom link string, and if so it doesn't append the rowid argument to the end of the string.
Update list.php
Merge pull request #793 from moofoo/patch-3

Update list.php