Lp1268743

While working on emulator testing, I managed to crash ofono as the emulator sometime response to SIM IO commands with a null response field.

My initial attempt to fix modified the low level reply parse function, but after testing and committing, I realized this would break the file-not-found logic which was added to ril_file_info_cb(), so I re-worked the fix to check for the zero length in the file_info_cb().

Tested on the emulator ( crash resolved ), and on mako ( verified GPRS, phone and text messages work ).