Fix the potential NullPointerException.

The networkAttributesParcelable retrieved from IpMemoryStore might be
null, it might cause crash with NullPointerException when attepmting
to read from the field on a null object reference.

Bug: 135174345
Test: atest FrameworksNetTests NetworkStackTests
Merged-In: I658fbba3e18c5c640ed7d445d2cd59c4221e055f
Merged-In: Ie6b5c293b4ca17622674d5f735a9d62e04410088

(cherry picked from commit 4769936f)

Change-Id: I3be6e57f6f8c56f828b025828aae0640248d23a9