Unsupported concepts can be selected when adding concept to a glossary

[cadamini]

The following message appears when I choose a subject field from the dropdown:

Specify only Subject fields that belong to the chosen glossary available subject fields.

Maybe it's useful to filter the list prior to presenting it to the user. If a concept is not supported, it should not appear here.

Reproduce it like this:

1. go to a glossary
2. click add a new concept to this glossary
3. select a concept from the subject field drop-down.

[unho]

@cadamini I am afraid this project is no longer maintained. Feel free to fork it, and fix this issue.