Sipe crashes when SfB peer starts sharing desktop while Pidgin is presenting

[xhaakon]

Skype for Business reuses existing session (same Call-Id) for its "applicationsharing" media. Sipe is not prepared for that.

[tcprdg]

@xhaakon how is this different from #59

[xhaakon]

@tcprdg in quite a lot of things:

• this happens only with Skype for Business. #59 is Pidgin -> Pidgin
• this crash happens under precisely reproducible conditions (while you are sharing your desktop, a SfB user starts sharing their own, thus becoming the presenting entity; this leads to a crash of Sipe)
• it has a known cause and I have at least a vague idea how to fix it.

(This ticket is mostly a note to myself. There's no further investigation needed to fix this unlike the other screen sharing crashes.)

[tcprdg]

ok, thanks!