Check for locking in tryToUnlockDocument:, avoid one unnecessary call of this method, small code changes
Check for locking in tryToUnlockDocument:, avoid one unnecessary call of this method, small code changes

JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim