Check for null in applyDefiningSharedLibraryUpdateLocked.

Handle two cases:
1) We haven't been able to create the shared library. The package manager
still installs the package, but doesn't create the shared library.

2) When installing a shared library, we update shared lib dependency
mappings before scanning. In the case that we're installing a
new shared library, we will not have reference to that shared library in
memory. This change adds a null check to account for such a scenario.

bug: 119438703
bug: 119497540
Test: atest android.os.cts.StaticSharedLibsHostTests#testAppCanSeeOnlyLibrariesItDependOnFullMode
Change-Id: I93d67f79ad0a58acd8cd4cb961cf82ada085821c