Fixed Crashing on 502 Issue
Fixed Crashing on 502 Issue

- Wrapped getting of header fields in a try catch
- Fixed issue where null NSError was causing a crash

CommuteStream/ios-sdk,CommuteStream/cs-ios-sdk,CommuteStream/ios-sdk,CommuteStream/cs-ios-sdk,CommuteStream/cs-ios-sdk,CommuteStream/cs-ios-sdk,CommuteStream/ios-sdk