Fix TextView#setTextCursorDrawable for resid=0

The CL fixes TextView#setTextCursorDrawable, for the case when a zero
drawable resource id is passed. We want to set a null Drawable, but the
Context#getDrawable(0) call was throwing rather than returning null.

Bug: 122742983
Test: atest CtsWidgetTestCases:android.widget.cts.TextViewTest
Change-Id: I45bf57002043d7dbe541d76e61fce3f729959fc8
1 file changed