Fix crash due to access of unretained value.
Fix crash due to access of unretained value.

For some reason the crash only occurs in some environments.

hamcrest/OCHamcrest,nschum/OCHamcrest,klundberg/OCHamcrest,klundberg/OCHamcrest,hamcrest/OCHamcrest,hamcrest/OCHamcrest,nschum/OCHamcrest,nschum/OCHamcrest