title: setValue:forKey crash with _sigtramp
body: <p>The trace is like this</p>
  
  <pre><code>Application received signal SIGSEGV
  
  Stack trace:
  #0  CoreFoundation                      002BCE149F &lt;redacted&gt;()
  #1  libobjc.A.dylib                     00394F8C8B objc_exception_throw()
  #2  CoreFoundation                      002BCE13E5 -[NSException initWithCoder:]
  #3  funadhoc                            000025B129 UmengSignalHandler()
  #4  libsystem_platform.dylib            0039BB8873 _sigtramp()
  #5  libobjc.A.dylib                     0039505571 objc_setProperty_nonatomic_copy()
  #6  Foundation                          002C947F59 -[NSObject setValue:forKey:]
  #7  Foundation                          002C9C58F3 -[NSObject setValuesForKeysWithDictionary:]
  ..........................
  </code></pre>
  
  <p>I understand the situation of <code>setValue:forUndefinedKey:</code> or <code>setNilValueForKey:</code> , but what is this?</p>
  
  <p>Besides, some system symbols are <code>&lt;redacted&gt;</code>, how can I get it symbolicated?</p>