[Phrases] Fragment generation does not work if no language is set

[galadhremmin]

JavaScript exception is thrown:

Uncaught (in promise) Error: Failed to parse fragments because language undefined does not exist!
    at SentenceActions_GlossActions.<anonymous> (common.js:2)
    at Generator.next (<anonymous>)
    at fulfilled (common.js:2)

Hide or disable the fragment UI if no language has been selected.