Parse.com crashes only on iOS7

Question

We have a crash on a real iPhone4, which only happens on iPhone4 (not iPhone6 ​​or the simulator).

The accident occurs here:

 PFQuery *getRelevantRows=[PFQuery queryWithClassName:@"Que"];
[getRelevantRows orderByDescending:@"updatedAt"];
getRelevantRows.limit=150;
//getRelevantRows.skip=skip;

 //query log has a value(number) here.

[getRelevantRows findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
//no log here.

in the line that finds the objects on the server.

Crash Report:

'NSInvalidArgumentException', reason: '*** setObjectForKey: key cannot be nil'

and its in line:

PfmultiProcessFileLockController

We use the latest SDKs for Parse. We can’t let go now, what could it be?