If PJSUA is built with video support, but all video codecs are disabled
(e.g. priority set to 0), making a call will fail due to assertion
(sdp_neg.c:111: pjmedia_sdp_neg_create_w_local_offer: Assertion
`(status=pjmedia_sdp_validate(local))==PJ_SUCCESS' failed.).
The reason seems to be that pjmedia_sdp_neg_create_w_local_offer()
expects at least one codec for each media line, but if video codecs are
disabled there are will be a media line for video but without any codec.
The problem is that in pjsua_media_channel_init() the codec priorities
(e.g. is there any active video codec registered?) are not taken into
account, only pjsua_call_setting is checked for call->opt.vid_cnt to
decide whether to add media line for video.
So is it really up to the user to also set vid_cnt in pjsua_call_setting
to 0 if codec priority of video codec has been set to 0 in codec manager?