Discard invalid key path

Environment variables such as ADB_VENDOR_KEYS can be set in a way that
Split function will return empty string. Example of problematic input
is ':./google/security/adb'.

Bug: NA
Test: NA
Flag: EXEMPT (adb.exe)

Change-Id: I4213c19b2e86815afd4a0b7872f647757fb2ea5a
1 file changed