Fix UDFPS enrolling crash

Bug: b/271208595
Test: 1. adb root
      2. adb shell setprop sys.fflag.override.settings_biometrics2_enrollment true
      3. Record fingerprint
      4. Check setting work normally
Change-Id: I69cc50cd677e80a57bb430a5a295c46b519d7755

src/com/android/settings/biometrics2/ui/widget/UdfpsEnrollView.java

@@ -226,6 +226,10 @@ public class UdfpsEnrollView extends FrameLayout {
         }
 
         DisplayInfo displayInfo = new DisplayInfo();
+        if (getDisplay() == null) {
+            android.util.Log.e(TAG, "Can not get display");
+            return;
+        }
         getDisplay().getDisplayInfo(displayInfo);
         Rect udfpsBounds = mSensorProperties.getLocation().getRect();
         float scaleFactor = mUdfpsUtils.getScaleFactor(displayInfo);