Crash in destroying pjsua with an active call and sound device managed by app (thanks Thomas Martin for the report).

[nanang]

Assertion (and sometimes access violations) when calling pjsua_destroy2(PJSUA_DESTROY_NO_NETWORK) in response to a network change (e.g. WiFi? to 3G or vice versa), if an incoming call happens to ring at that moment.

Assertion:

Assertion failed: (mutex->owner == pj_thread_this()),
function pj_mutex_unlock, file ../src/pj/os_core_unix.c, line 1256.

Crash callstack trace:

#0	0x00081410 in pjmedia_conf_get_connect_count ()
#1	0x00054dbe in check_snd_dev_idle ()
#2	0x00055f3a in pjsua_media_channel_deinit ()
#3	0x00057be8 in pjsua_media_subsys_destroy ()
#4	0x000510e4 in pjsua_destroy2 ()

[nanang]

(In [3981]) Re #1467: fix sound device (opened/closed) status check in check_snd_dev_idle(), especially when sound device is managed by app (no_snd = PJ_TRUE). Note that pjsua_media_subsys_destroy() always close the sound device first, so check_snd_dev_idle() in pjsua_destroy() sequence should have been just a no-operation.

[nanang]

The assertion is not reproducible, for now let's just assume this is a stray event which may be caused by other pjsua restart issues (e.g: #1470, #1471).