couchbase-lite-ios: PSWebSocket crash iOS 10

I can’t reproduce this, but it is a common crash (especially given the low usage of iOS10) in our released app.

Raw stack…

#9. Crashed: PSWebSocket <https://<url removed>/db/_changes?feed=websocket>
0  libdispatch.dylib              0x181c098f0 _dispatch_barrier_sync_f_slow + 596
1  Concepts                       0x100619c98 BLIPEncodeProperties + 619860
2  Concepts                       0x100619c98 BLIPEncodeProperties + 619860
3  libsystem_blocks.dylib         0x181c4ea28 _Block_release + 144
4  libdispatch.dylib              0x181bf5018 _dispatch_client_callout + 16
5  libdispatch.dylib              0x181c06e84 _dispatch_queue_serial_drain + 928
6  libdispatch.dylib              0x181bf8808 _dispatch_queue_invoke + 652
7  libdispatch.dylib              0x181c07380 _dispatch_queue_override_invoke + 360
8  libdispatch.dylib              0x181c08d1c _dispatch_root_queue_drain + 572
9  libdispatch.dylib              0x181c08a7c _dispatch_worker_thread3 + 124
10 libsystem_pthread.dylib        0x181dff3f8 _pthread_wqthread + 1276
11 libsystem_pthread.dylib        0x181dfeef0 start_wqthread + 4

There is also the following entry in the crash report…

“CRASH_INFO_ENTRY_0 BUG IN CLIENT OF LIBDISPATCH: dispatch_barrier_sync called on queue already owned by current thread”

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• Version: 1.2.1
• Client OS: 10.0.0 (14A5297c) and 10.0.0 (14A5261v)
• Server: sync_gateway 1.2.1