Bug#921266: The segfault Is defintely not caused by t-online, but linpone

[Alf]

I have done further tests and finally given up to get linphone working
as a SIP client here - the segfault on password enty is absolutely
reproducible.

To solve this issue I have tried "twinkle" (another SIP client from
Buster-repo and that was set up within a few minutes.
Just entered the SIP and STUN servers and my credentials for my t-online
account - and all works as expected.

This definitely confirms that it is not related to t-online, nor to some
missconfiguration of my system.

Moreover such a segfault is caused by severe bugs in the application
itself. Again the syslog message:

tux kernel: [ 4866.131680] linphone[6107]: segfault at 0 ip
0000003153a8f37a sp 00007ffe572604c8 error 4 in
libc-2.24.so[3153a00000+194000]
Mar  3 18:17:33 tux kernel: [ 4866.131690] Code: 89 e6 5b 4c 89 ef 5d 41
5c 41 5d e9 e0 49 ff ff 89 f8 31 d2 66 0f ef ff 09 f0 25 ff 0f 00 00 3d
c0 0f 00 00 0f 8f 78 02 00 00 <f3> 0f 6f 0f f3 0f 6f 06 66 0f 74 c1 66
0f da c1 66 0f ef c9 66 0f

of which the tail is always the same:
-------------------------------------
... 89 f8 31 d2 66 0f ef ff 09 f0 25 ff 0f 00 00 3d c0 0f 00 00 0f 8f 78
02 00 00 <f3> 0f 6f 0f f3 0f 6f 06 66 0f 74 c1 66 0f da c1 66 0f ef c9 66 0f

 There is also no means to gather more info about the crash in libc6
besides the syslog entry. Linphone's debug output.
Even at highest level does not disclose anything valuable for me.

So linphone 3.12 from Buster is buggy and absolutely unusable for me,
severity should be set back to 'serious' to reflect that.