PackageUtil: don't collect certs if package doesn't exist

If packageParser.parsePackage() returns null, don't attempt call
packageParser.collectCertificates().

This fixes a NPE triggered by the following command:

am start -a android.intent.action.VIEW -d file:///blah/blah.apk -t application/vnd.android.package-archive

Change-Id: I6f6f836734d4b4ee07e98ee6b1f6339fa675b8b0
1 file changed