PhoneStatusBar: Add test for executeRunnableDismissingKeyguard with null runnable

Adds a regression test for NPEs around executeRunnableDismissingKeyguard when
a null runnable is passed.

The bug was fixed in I89477a8a0067e285e5d0122e918fac45274c57ad.

Fixes: 33489225
Test: runtest systemui
Change-Id: Ia8981bc4c2a1a0f6d8c48e6d66e2af801d6cddac
1 file changed