It's failing on let titleResult

I tried running my Code which "guard let" and "do catch" This Time, They are successful. I didn't edit any code. It's Same Satuts, Same Device But sometimes trapping thought "Thread 1: Swift runtime failure: Unexpectedly found nil while implicitly unwrapping an Optional value" I don't know why trapping thought error. It's same code, same satus, same device..... Thank you your answer