Do not treat NULL response as error for getAllowedCarriers

NULL is a valid response in RIL_REQUEST_GET_CARRIER_RESTRICTIONS
as per RIL.h. NULL implies all carriers are allowed. This fix skips
setting error if response is NULL to fix VTS failure.

Test: VTS
Bug: 37849113
Bug: 37157801
Change-Id: Ida3d2d0f10693ed396b236ac9512afb277ce2ddb
1 file changed
tree: 8036acd3fa98b00ee11c38c9ec03fcc631f62156
  1. include/
  2. libril/
  3. librilutils/
  4. reference-ril/
  5. rild/
  6. CleanSpec.mk