Prevent NULL deref in uninitialized nativehelper

Bug: 174768641
Test: atest MediaTrackTranscoderTests
Test: Invocation of JNI_GetCreatedJavaVMs before JniInvocation init.
Change-Id: Icd4c4a65cc6a933671a54242df7f3aed07053baa
Merged-In: Icd4c4a65cc6a933671a54242df7f3aed07053baa
3 files changed