Remove invalid null check for callingPackage

getLaunchedFromPackage() will never return null. As such, remove the
null check while processing a session based install

Bug: 399881067
Bug: 364604008
Test: atest CtsPackageInstallTestCases CtsAppOps2TestCases

Merged-In: I8d08eb6de72f4ac2f5ac0a5c0fef26cc0578f8e9
Change-Id: I86c8f2e9bccb9a0f8ee7ec29bd3e79dbfa05e9da