New blank dictionary with primary language Thai - input systems set up wrong

[rmunn]

If I create a new Dictionary project with the primary language as Thai (th), it results in a blank language code for new words in the lexicon, and the dictionary configuration shows the Thai writing system as either blank or non-existent. (E.g., click on Dictionary Configuration, and the Input Systems tab shows only English and no other systems. Click over to the Fields tab and there are two writing systems, "" and "en". The blank one is the one that should be Thai).

This doesn't happen with any other primary languages (as far as I've determined), just with Thai (th).