Update merge error message

[jamiefolsom]

Something is preventing merging of some records, but it's not clear what. I suspect the "Autres Informations" fields, containing "? Even excluding those values, however, I get this error.

[dleadbetter]

This was happening due to a required field on one of the relationships that did not contain any data for some records (due to being created as part of the import). The temporary solution was to simply make the field not required. As a more long term solution, we should update the error message to be something more meaningful than "is invalid". Moving back to "New Issues" to address at a later time.