crash after disconnect and switch accounts

[SURENDRA7700]

14:06:48.425 os_core_unix.c !pjlib 2.2.1-svn for POSIX initialized
14:06:48.427 sip_endpoint.c .Creating endpoint instance...
14:06:48.428 pjlib .select() I/O Queue created (0x13e858a28)
14:06:48.428 sip_endpoint.c .Module "mod-msg-print" registered
14:06:48.428 sip_transport. .Transport manager created.
14:06:48.428 pjsua_core.c .PJSUA state changed: NULL --> CREATED
14:06:48.504 pjsua_core.c .pjsua version 2.2.1-svn for initialized
2016-07-25 14:07:18.275 GossipExample[2253:1291601] Gossip: dispatchRegistrationStarted(0, 1)
14:07:27.774 pjsua_acc.c .Unable to create/send REGISTER: Object is busy (PJSIP_EBUSY) [status=171001]
2016-07-25 14:07:27.774 GossipExample[2253:1291601] Gossip: Error Domain=pjsip.org Code=341001 "Object is busy (PJSIP_EBUSY)" UserInfo={PJSIP_ERRNO_FORM_SIP_STATUS=341001, NSLocalizedDescription=Object is busy (PJSIP_EBUSY), pj_status_t=171001}
2016-07-25 14:07:27.775 GossipExample[2253:1291601] Destroying...
14:07:27.777 pjsua_acc.c ..Unable to create/send REGISTER: Object is busy (PJSIP_EBUSY) [status=171001]
14:07:32.278 pjsua_acc.c ....SIP registration failed, status=503 (Service Unavailable)
2016-07-25 14:07:32.279 GossipExample[2253:1291601] Gossip: dispatchRegistrationState(0)
2016-07-25 14:07:32.814 GossipExample[2253:1291601] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'An instance 0x13de6fd70 of class GSAccount was deallocated while key value observers were still registered with it. Current observation info: <NSKeyValueObservationInfo 0x13ddae1d0> (
<NSKeyValueObservance 0x13de64550: Observer: 0x13de308b0, Key path: status, Options: <New: NO, Old: NO, Prior: NO> Context: 0x0, Property: 0x13de31610>
)'
*** First throw call stack:
(0x181e7edb0 0x1814e3f80 0x181e7ecf8 0x1827d2d80 0x10003bb20 0x1871d96fc 0x1819258e8 0x1872f3d3c 0x1814e2b54 0x1814ee040 0x1814ee0a0 0x181d67ee0 0x1814fdae8 0x181d5c9fc 0x181e32bc0 0x181d5cc50 0x183644088 0x187046088 0x10003a184 0x1818fa8b8)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)