[1.x] crash on videoroom

[spscream]

What version of Janus is this happening on?
we got this on fork from master(so lines of gdb dump isn't match current master).

Have you tested a more recent version of Janus too?
checked on fork from latest master

Was this working before?
no info

Is there a gdb or libasan trace of the issue?
(gdb) bt
#0 0x00007fbe88e17485 in janus_videoroom_hangup_media_internal (session_data=session_data@entry=0x7fbe878735c0) at plugins/janus_videoroom.c:9717
#1 0x00007fbe88e18e98 in janus_videoroom_hangup_media (handle=) at plugins/janus_videoroom.c:9674
#2 0x0000564d912498d0 in janus_ice_outgoing_traffic_handle (handle=0x7fbe831cdb20, pkt=0x564d912c7840 <janus_ice_hangup_peerconnection>) at ice.c:4631
#3 0x0000564d9124cd41 in janus_ice_outgoing_traffic_dispatch (source=0x7fbe85cef490, callback=, user_data=) at ice.c:528
#4 0x00007fbe8a33f255 in ?? () from /usr/lib/libglib-2.0.so.0
#5 0x00007fbe8a342387 in ?? () from /usr/lib/libglib-2.0.so.0
#6 0x00007fbe8a342c77 in g_main_loop_run () from /usr/lib/libglib-2.0.so.0
#7 0x0000564d9123e2c8 in janus_ice_handle_thread (data=0x7fbe831cdb20) at ice.c:1354
#8 0x00007fbe8a3725f0 in ?? () from /usr/lib/libglib-2.0.so.0
#9 0x00007fbe8a72e34f in start (p=0x7fbe682228e8) at src/thread/pthread_create.c:207
#10 0x00007fbe8a730965 in __clone () at src/thread/x86_64/clone.s:22

some investigation shows what ss->subscriber contains random data in memory, so it used after free:

(gdb) x/4s ss->subscriber
0x7fbe877587f0: "{\n   \"janus\": \"event\",\n   \"session_id\": 4487988242871326,\n   \"sender\": 3600588038572687,\n   \"plugindata\": {\n    ! \"plugin\": \""
0x7fbe8775886e: ""
0x7fbe8775886f: ""
0x7fbe87758870: ""

Additional context
We've got this crash on different customers randomly from time to time. And i've made some fix - on version with fix it doesn't crash. I'll attach pr with possibly fix.