Make InputFilter.AllCaps constructor reject null locales

In I021ff2a97a60396fb1b6e4940d91d3cd6ccb6196, new API for
InputFilter.AllCaps was added. It accepted null as input. This CL
changes that so null locales would be rejected.

Test: bit CtsTextTestCases:android.text.cts.InputFilter_AllCapsTest
Fixes: 64261334
Bug: 37222101

Change-Id: Ic87942c3f341f71bc3c1c833b52ea3e751461e47
1 file changed