SIGABRT error in iOS

Hi all,

I am beta testing my app (“trucktrials.com”) and one of my testers has an error on his device.   I am using hockeyapp to beta test, and when I imported the test log (hockey.txt attached) into xcode I can see (hockeySym.txt attached);

Exception Type: SIGABRT Exception Codes: #0 at 0x24d7ec5c Crashed Thread: 0 Application Specific Information: \*\*\* Terminating app due to uncaught exception 'Corona Runtime Error', reason: 'attempt to index upvalue '?' (a nil value)'

When I test the app on my device I cannot recreate the error, and with this error message it is very hard to track.  On the upside according to the log the user has been playing for 23 minutes before the error occured, so not too bad…

Can anyone shed some light on how I can go about finding and eliminating this error?

Thanks,

Craig