title: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
body: <p>I really can't figure out why I have this bug.</p>
  <p>First of all the debugger stop at machine code</p>
  <p><img src="https://i.stack.imgur.com/9U7hL.jpg" alt="enter image description here" /></p>
  <p>The thread also shows nothing. The program stop at no code actually</p>
  <p><img src="https://i.stack.imgur.com/VBLpB.jpg" alt="enter image description here" /></p>
  <p>So  it has something to do with _dispatch_worker_thread</p>
  <p>What is that?</p>
  <p>Any way how I can debug this? Should I just rollback?</p>