Null check ApplicationInfo for ApplicationPackageManager#loadUnbadgedItemIcon

Broken by I55026af543ff71ac0d947159bc6aeb3b33f31271 which added a shortcut.
Really caused by the method not being annotated correctly so it was
non-obvious that the AppInfo could be null.

Bug: 132078158

Test: atest PackageItemInfoIconTest

Change-Id: Ifd2789a80d2dad86ba4e09b1d9220ecab5d612ec