crash when removing/modifying trackers

[livings124]

A crash appears to occur for some users when removing or modifying the tracker list. This is possibly a threading issue, where the list is modified while in use.

Forum thread: ​http://forum.transmissionbt.com/viewtopic.php?f=4&t=9177

Another crash log (from wereHamster): ​http://pastie.org/764187

[charles]

Money quote:

Thread 2 Crashed:
0   libSystem.B.dylib             	0x00007fff826d4dd1 strchr + 6
1   org.m0k.transmission          	0x00000001000c5647 tierScrape + 410 (announcer.c:1555)
2   org.m0k.transmission          	0x00000001000c5de4 announceMore + 1196 (announcer.c:1649)
3   org.m0k.transmission          	0x00000001000c6077 onUpkeepTimer + 51 (announcer.c:1708)
4   org.m0k.transmission          	0x00000001000d5653 event_process_active + 303 (event.c:393)
5   org.m0k.transmission          	0x00000001000d59fb event_base_loop + 462 (event.c:545)
6   org.m0k.transmission          	0x00000001000d582b event_loop + 35 (event.c:469)
7   org.m0k.transmission          	0x00000001000d56a2 event_dispatch + 20 (event.c:407)
8   org.m0k.transmission          	0x000000010009b31f libeventThreadFunc + 205 (trevent.c:227)
9   org.m0k.transmission          	0x000000010008a4e6 ThreadFunc + 43 (platform.c:114)
10  libSystem.B.dylib             	0x00007fff826f5f8e _pthread_start + 331
11  libSystem.B.dylib             	0x00007fff826f5e41 thread_start + 13

[charles]

looks like the session mutex should fix this. fixed in trunk for 1.80 by r9860.