Crypto: Crash in key backup

[manuroe]

There is something weird in the key we are trying to backup or with the key backup key.

Last Exception Backtrace:
0   CoreFoundation                      0x1a186586c __exceptionPreprocess + 220 (NSException.m:199)
1   libobjc.A.dylib                     0x1b67d4c50 objc_exception_throw + 60 (objc-exception.mm:565)
2   CoreFoundation                      0x1a18d5e1c _CFThrowFormattedException + 116 (CFObject.m:1994)
3   CoreFoundation                      0x1a18e2270 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:].cold.4 + 52 (NSPlaceholderDictionary.m:70)
4   CoreFoundation                      0x1a1756550 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:] + 308 (NSPlaceholderDictionary.m:0)
5   CoreFoundation                      0x1a1748dd0 +[NSDictionary dictionaryWithObjects:forKeys:count:] + 60 (NSDictionary.m:607)
6   MatrixSDK                           0x1065f8ed0 0x106544000 + 741072 -> -[MXKeyBackup encryptGroupSession:] (in MatrixSDK) (MXKeyBackup.m:0)
7   MatrixSDK                           0x1065f10c4 0x106544000 + 708804 -> -[MXKeyBackup sendKeyBackup] (in MatrixSDK) (MXKeyBackup.m:0)
8   MatrixSDK                           0x1065f0e3c 0x106544000 + 708156 -> __33-[MXKeyBackup maybeSendKeyBackup]_block_invoke (in MatrixSDK) (MXKeyBackup.m:0)
9   libdispatch.dylib                   0x1a1459db0 _dispatch_client_callout + 20 (object.m:559)
10  libdispatch.dylib                   0x1a145d12c _dispatch_continuation_pop + 416 (inline_internal.h:2548)
11  libdispatch.dylib                   0x1a146ec08 _dispatch_source_invoke + 1260 (source.c:570)
12  libdispatch.dylib                   0x1a1460fd8 _dispatch_lane_serial_drain + 272 (inline_internal.h:2589)
13  libdispatch.dylib                   0x1a1461c5c _dispatch_lane_invoke + 408 (queue.c:3862)
14  libdispatch.dylib                   0x1a146bd78 _dispatch_workloop_worker_thread + 708 (queue.c:6601)
15  libsystem_pthread.dylib             0x1ed037804 _pthread_wqthread + 276 (pthread.c:2207)
16  libsystem_pthread.dylib             0x1ed03e75c start_wqthread + 8