getTelephonyProperty returns defaultVal

getTelephonyProperty needs to return defaultVal, which it currently
doesn't because SystemProperties.get doesn't return null, it returns
empty-string.

Change-Id: Ida06d3c4ce46a9e988ca7a2b0677293fb6a932eb
Fixes: 113796156
Test: atest FrameworksTelephonyTests
1 file changed