Fix null pointer exception when getting app label for headless app

Will follow up with regression test in CrossProfileAppsTest cts
test.

Test: Manual - screenshots in bug
Test: atest frameworks/base/core/tests/coretests/src/android/content/pm/CrossProfileAppsTest.java
Bug: 295888390
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:6249cd22da9bc6ac905faf7a0e09a67680b37969)
Merged-In: I2c95a73434fa724f69a945809106e4de3b59a6ba
Change-Id: I2c95a73434fa724f69a945809106e4de3b59a6ba