Guard against the exceptions when launching a non-existing fragment

Test: robotest
Bug: 190371550
Change-Id: I2bb7d4bdb23756634526db7e272563a1587c9640

src/com/android/settings/SettingsActivity.java

@@ -574,7 +574,7 @@ public class SettingsActivity extends SettingsBaseActivity
     /**
      * Switch to a specific Fragment with taking care of validation, Title and BackStack
      */
-    private Fragment switchToFragment(String fragmentName, Bundle args, boolean validate,
+    private void switchToFragment(String fragmentName, Bundle args, boolean validate,
             int titleResId, CharSequence title) {
         Log.d(LOG_TAG, "Switching to fragment " + fragmentName);
         if (validate && !isValidFragment(fragmentName)) {
@@ -582,6 +582,9 @@ public class SettingsActivity extends SettingsBaseActivity
                     + fragmentName);
         }
         Fragment f = Utils.getTargetFragment(this, fragmentName, args);
+        if (f == null) {
+            return;
+        }
         FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
         transaction.replace(R.id.main_content, f);
         if (titleResId > 0) {
@@ -592,7 +595,6 @@ public class SettingsActivity extends SettingsBaseActivity
         transaction.commitAllowingStateLoss();
         getSupportFragmentManager().executePendingTransactions();
         Log.d(LOG_TAG, "Executed frag manager pendingTransactions");
-        return f;
     }
 
     private void updateTilesList() {