Ios AFJSONResponseSerializer ResponseObject ForResponse发生崩溃：数据：错误：

这个崩溃发生在iOS8.X，我不知道为什么，请帮我解决这个问题，打击是崩溃堆栈，AFNetworking的lib是2.5.0，阅读代码proplen发生在这一行

Operating system: iOS
              8.3.0 12F70
CPU: arm64
 2 CPUs

Crash reason:  EXC_SOFTWARE / SIGABRT
Crash address: 0x193ea3270

Thread 35 (crashed)
 0  libsystem_kernel.dylib!__pthread_kill + 0x8
    Found by: given as instruction pointer in context
 1  libsystem_pthread.dylib!pthread_kill + 0x6c
    Found by: previous frame's frame pointer
 2  libsystem_c.dylib!abort + 0x6c
    Found by: previous frame's frame pointer
 3  libsystem_malloc.dylib!nanozone_error + 0x13c
    Found by: previous frame's frame pointer
 4  libsystem_malloc.dylib!nano_realloc + 0x3fc
    Found by: previous frame's frame pointer
 5  libsystem_malloc.dylib!malloc_zone_realloc + 0x78
    Found by: previous frame's frame pointer
 6  CoreFoundation!__CFStringCreateImmutableFunnel3 + 0x518
    Found by: previous frame's frame pointer
 7  CoreFoundation!CFStringCreateFromExternalRepresentation + 0x64
    Found by: previous frame's frame pointer
 8  Foundation!-[NSPlaceholderString initWithData:encoding:] + 0x8c
    Found by: previous frame's frame pointer
 9  Mobile!-[AFJSONResponseSerializer     responseObjectForResponse:data:error:] [AFURLResponseSerialization.m : 253 + 0x10]
    Found by: previous frame's frame pointer
10  Mobile!__72-[AFURLSessionManagerTaskDelegate     URLSession:task:didCompleteWithError:]_block_invoke69 [AFURLSessionManager.m : 179 + 0x1c]
    Found by: previous frame's frame pointer
 11  libdispatch.dylib!_dispatch_call_block_and_release + 0x14
    Found by: previous frame's frame pointer

  @autoreleasepool {
    NSString *responseString = [[NSString alloc] initWithData:data encoding:stringEncoding];