jsonmodel: Crashes in JSONModel.m line 855 (reason unknown)

Since using JSONModel 1.2.0 our app is regularly reporting crashes in JSONModel dictionary deserialization. To be specific, the crashes happen in __customSetValue:forProperty:.

Sadly, I cannot provide any data that reproduces the error, but maybe the author can find any possible problem in this code.

Here is the respective call stack of one such crash:

Thread : Crashed: com.apple.root.default-qos
0  libobjc.A.dylib                0x3958df62 objc_msgSend + 1
1  CoreFoundation                 0x2b00a17d -[__NSDictionaryM setObject:forKey:] + 340
2  App                            0x2a316b __arclite_NSMutableDictionary__setObject_forKeyedSubscript(NSMutableDictionary*, objc_selector*, objc_object*, objc_object*) (arclite.mm:1669)
3  App                            0x1d2bed -[JSONModel __customSetValue:forProperty:] (JSONModel.m:855)
4  App                            0x1d0b7b -[JSONModel __importDictionary:withKeyMapper:validation:error:] (JSONModel.m:342)
5  App                            0x1cfbd9 -[JSONModel initWithDictionary:error:] (JSONModel.m:191)
6  App                            0x1d3a15 +[JSONModel arrayOfModelsFromDictionaries:error:] (JSONModel.m:1124)
7  App                            0x1bb4dd __68-[AppService service:success:failure:]_block_invoke_2 (AppService.m:21)
8  libdispatch.dylib              0x39b11c83 _dispatch_call_block_and_release + 10
9  libdispatch.dylib              0x39b1e86b _dispatch_root_queue_drain + 1374
10 libdispatch.dylib              0x39b1f8a3 _dispatch_worker_thread3 + 106
11 libsystem_pthread.dylib        0x39c93d9d _pthread_wqthread + 668
12 libsystem_pthread.dylib        0x39c93af0 start_wqthread + 8