Check aid against empty string for SIM_REFRESH

The new RIL in O changes all null strings to empty strings, but the code
in uicc only checks aid against null for SIM_REFRESH. This CL adds the
check against empty strings.

Bug: 34650917
Test: build
Change-Id: I4883def3b0dcf3f505941297d458a607db54f300
4 files changed