Catch WindowManager exceptions so they don't crash the system.

WindowManager throws an IllegalStateException when adding a view twice; this
should never happen (since show() and hide() are always called in the UIThread),
but when it does, it should not crash the system.

Test: existing CtsAutoFillServiceTestCases pass
Fixes: 62262781

Change-Id: Idfd246ff173f4abb606865b7ba8cc367eb6acaad