Expected result: The person at extension XXX is unavailable ...
Actual result: The person at is unavailable...
i.e. it doesn't say the extension number.
bug: trying to access local variable voicemail_greet_id outside it's scope...so it doesn't exist and you get this in the logs:
2016-09-18 12:32:54.615249 [ERR] switch_cpp.cpp:977 Error! invalid args.
Fix moves local variable creation outside the inner "if" so it's available for the later table.insert