Changing word replacement strings does not work if you have more than one set in civicrm_domain

In our CiviCRM instance, we have two sets of word replacement strings in civicrm_domain. One for en_US, and one for nl_NL. In our case, this is just a misconfiguration, but I can imagine that in some cases this is useful.

Now if you do have more than one set, it is possible that you cannot change existing word replacement strings.

I have a patch for this, which I will upload in a moment.