what does Error “Thread 1:EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)” mean?

Question

I got this error:

Thread 1:EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

How can I solve this? The code works normally,

Answer 1

Mine was about

dispatch_group_leave(group)

was inside if closure in block. I just moved it out of closure.