Native iOS Map module crashes with uncaught exception 'NSInvalidArgumentException'

I am toggling between two sets of map annotations, one shows up fine, the other one doesn't show at all (sometimes causing the crashing instantly, sometimes seconds later). Running Ti SDK 3.5.0.GA and ti.map module 2.2.0.

Any leads on what "unrecognized selector sent to instance" means?

Thanks.

[ERROR] The application has crashed with an uncaught exception 'NSInvalidArgumentException'.
[ERROR] Reason:
[ERROR] -[NSNull length]: unrecognized selector sent to instance 0x35f986a0
[ERROR] Stack trace:
[ERROR]   
[ERROR] 0   CoreFoundation                      0x27ef45f7 <redacted> + 126
[ERROR] 1   libobjc.A.dylib                     0x3562ec77 objc_exception_throw + 38
[ERROR] 2   CoreFoundation                      0x27ef9abd <redacted> + 0
[ERROR] 3   CoreFoundation                      0x27ef7999 <redacted> + 712
[ERROR] 4   CoreFoundation                      0x27e28b88 _CF_forwarding_prep_0 + 24
[ERROR] 5   MapKit                              0x295f5655 <redacted> + 388
[ERROR] 6   MapKit                              0x2960eb15 <redacted> + 212
[ERROR] 7   MapKit                              0x2960eef7 <redacted> + 330
[ERROR] 8   UIKit                               0x2b3ceb83 <redacted> + 146
[ERROR] 9   UIKit                               0x2b3cea3d <redacted> + 832
[ERROR] 10  UIKit                               0x2b3c24e1 <redacted> + 508
[ERROR] 11  UIKit                               0x2b3c22ad <redacted> + 152
[ERROR] 12  UIKit                               0x2b60c90f <redacted> + 13214
[ERROR] 13  UIKit                               0x2b397b27 <redacted> + 1294
[ERROR] 14  CoreFoundation                      0x27ebafd7 <redacted> + 14
[ERROR] 15  CoreFoundation                      0x27eba3eb <redacted> + 222
[ERROR] 16  CoreFoundation                      0x27eb8a69 <redacted> + 768
[ERROR] 17  CoreFoundation                      0x27e05b31 CFRunLoopRunSpecific + 476
[ERROR] 18  CoreFoundation                      0x27e05943 CFRunLoopRunInMode + 106
[ERROR] 19  GraphicsServices                    0x2f1bc051 GSEventRunModal + 136
[ERROR] 20  UIKit                               0x2b3f7f21 UIApplicationMain + 1440
[ERROR] 21  Waterbowl                           0x000aee7f Waterbowl + 20095
[ERROR] 22  libdyld.dylib                       0x35bcaaaf <redacted> + 2
[ERROR] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull length]: unrecognized selector sent to instance 0x35f986a0'
[ERROR] *** First throw call stack:
[ERROR] (0x27ef45f7 0x3562ec77 0x27ef9abd 0x27ef7999 0x27e28b88 0x295f5655 0x2960eb15 0x2960eef7 0x2b3ceb83 0x2b3cea3d 0x2b3c24e1 0x2b3c22ad 0x2b60c90f 0x2b397b27 0x27ebafd7 0x27eba3eb 0x27eb8a69 0x27e05b31 0x27e05943 0x2f1bc051 0x2b3f7f21 0xaee7f 0x35bcaaaf)