Fix permission bypasses to multiple methods

Researcher reports that some BT calls across Binder are validating only
BT's own permissions and not the calling app's permissions.  On
investigation this seems to be due to a missing null check in several BT
permissions checks, which allows a malicious app to pass in a null
AttributionSource and therefore produce a stub AttributionSource chain
which does not properly check for the caller's permissions.

Add null checks.

Bug: 242996380
Test: atest UtilsTest
Test: researcher POC
Tag: #security
Ignore-AOSP-First: Security
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:244e4734d1ed316e8725b0f33e18d8eb709554f1)
Merged-In: I57d80cfa07bd6d3fd410a01764b3db2db9b41b81
Change-Id: I57d80cfa07bd6d3fd410a01764b3db2db9b41b81