Derp, that's what I get for not paying attention when copying stuff over. Actually, what I usually do is `- (NSArray *)__attribute__((nonnull(1, 2)))tryFetchRequest:(NSFetchRequest *)request error:(void (^)(NSError *error))errorBlock` and then don't worry about checking for nil when executing blocks, but forgot it here.

I will add it in here though, since you allow passing nil in other blocks.