Clean injection dependency to PipMenuActivity (4/N)

1) PipMenuIconsAlgorithm only used by PipMenuActivity,
   break that DI for the following migration

2) Add Null check to prevent NPE in handleMessage()

Bug: 161118569
Test: make SystemUI
Test: make ArcSystemUI
Test: make CarSystemUI
Test: atest WindowManagerShellTests
Test: atest SystemUITests
Change-Id: Ibf472b30a5210a6663bd43c20b8d4c1e6930779b