Fix crash in ChooseLockGenericFragment.

- in onActivityResult(), the intent data can be null. Check for non null
intent data before trying to read the extra string from the intent.

Change-Id: I14c42725a7885a84688ae39fde63e30ad0536001
Fixes: 109675331
Test: make RunSettingsRoboTests

tests/robotests/src/com/android/settings/password/ChooseLockGenericTest.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package com.android.settings.password;
+
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.Mockito.doNothing;
+import static org.mockito.Mockito.spy;
+
+import android.app.Activity;
+import com.android.settings.password.ChooseLockGeneric.ChooseLockGenericFragment;
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+public class ChooseLockGenericTest {
+
+    @Test
+    public void onActivityResult_nullIntentData_shouldNotCrash() {
+        ChooseLockGenericFragment fragment = spy(new ChooseLockGenericFragment());
+        doNothing().when(fragment).updatePreferencesOrFinish(anyBoolean());
+
+        fragment.onActivityResult(
+                fragment.CONFIRM_EXISTING_REQUEST, Activity.RESULT_OK, null /* data */);
+        // no crash
+    }
+
+}