Fix NPE: due to race condition between KCM package update

Not reproducible bug, possible cause of the bug is Gboard
package getting updated while PK connected causing the keyboard
notification using stale KCM descriptor which points to no KCM file.

Bug: 349033234
Test: None
Flag: EXEMPT bugfix
Change-Id: I946848ab7b03945c9c1a234a18ba8ca9db3c86e6