Fix NPE in InsertionPointCursorController.onTouchEvent

Calls to SelectionModifierCursorController must be guarded by
hasSelectionController() because it's possible to have a TextView
with an Editor but no selection controller if the TextView is
configured to have non-selectable text.

Bug: 147366705
Bug: 145535274
Bug: 143852764
Test: Manual and unit test
  atest FrameworksCoreTests:EditorCursorDragTest
Change-Id: I7fdec754e6fa51561b08fab024ea672c43f2c8f5