Don't update UI if getActivity returns null

Flag: EXEMPT minor fix
Test: local test
Bug: 383016400
Change-Id: I4d62da1a6d74db18f2c7cd20eb2e5b3825556fc5

src/com/android/settings/bluetooth/BluetoothDeviceDetailsFragment.java

@@ -136,7 +136,8 @@ public class BluetoothDeviceDetailsFragment extends RestrictedDashboardFragment
             (device, key, value) -> {
                 if (key == METADATA_FAST_PAIR_CUSTOMIZED_FIELDS
                         && mExtraControlViewWidth > 0
-                        && !mExtraControlUriLoaded) {
+                        && !mExtraControlUriLoaded
+                        && getActivity() != null) {
                     Log.i(TAG, "Update extra control UI because of metadata change.");
                     updateExtraControlUri(mExtraControlViewWidth);
                 }