Incoming OPTIONS may trigger assertion if it arrives when PJSUA-LIB is being shutdown (thanks Johan Lantz for the report)

[bennylp]

When an OPTION request arrives while PJSUA-LIB is being shutdown, it may trigger assertion error depending on the timing of the request. This is because the media endpoint has been destroyed.

The assertion:

*** ASSERTION FAILED in ..\src\pjmedia\endpoint.c(304):
endpt && pool && p_sdp && stream_cnt

Thanks Johan Lantz for the report.

[bennylp]

In r2871:

• destroy the media subsystem after busy_sleep(1000) in the shutdown sequence
• also handle the case when OPTIONS arrives just when PJSUA-LIB is being initialized and media transport is not ready (in this case just reply OPTIONS without message body)