Fix NullPointerException when renaming a fingerprint

(Original change made by xingbin.feng@sony.com)

Fix NullPointerException when rotating the screen while renaming
a registered fingerprint

Bug: 236873593
Test: Click a registered fingerprint to open the Rename dialog,
rotate the device and press OK. Verify that Settings does not
crash

Change-Id: I1350c4bd121e0a7aaa291b3b8f96c80ef777150b