Fix npe verifying perms
Fixed a NPE for apps with no permissions.
Here is an example of the logging output for a couple of apps too after my change:
D/ApkVerifier(10929): Checking permissions
D/ApkVerifier(10929): Actual:
D/ApkVerifier(10929): None
D/ApkVerifier(10929): Expected:
D/ApkVerifier(10929): None
and
D/ApkVerifier(10929): Checking permissions
D/ApkVerifier(10929): Actual:
D/ApkVerifier(10929): android.permission.READ_EXTERNAL_STORAGE
D/ApkVerifier(10929): android.permission.WRITE_EXTERNAL_STORAGE
D/ApkVerifier(10929): android.permission.SET_WALLPAPER
D/ApkVerifier(10929): android.permission.SET_WALLPAPER_HINTS
D/ApkVerifier(10929): android.permission.WRITE_SETTINGS
D/ApkVerifier(10929): Expected:
D/ApkVerifier(10929): android.permission.SET_WALLPAPER
D/ApkVerifier(10929): android.permission.READ_EXTERNAL_STORAGE
D/ApkVerifier(10929): android.permission.SET_WALLPAPER_HINTS
D/ApkVerifier(10929): android.permission.WRITE_SETTINGS
D/ApkVerifier(10929): android.permission.WRITE_EXTERNAL_STORAGE