Don't crash on opening ejecting USB.

This crash occurs because, even if you finish an Activity during
onCreate, the other lifecycle methods occur. In this case,
onActivityCreated assumes that onCreate ran properly.

By exiting early from onActivityCreated, we can ensure the activity
is finished properly.

Change-Id: Ia354341bf82d295c7dd042668fb11d588ddfebc0
Fixes: 37334861
Test: Instrumentation test

src/com/android/settings/deviceinfo/PublicVolumeSettings.java

@@ -98,7 +98,9 @@ public class PublicVolumeSettings extends SettingsPreferenceFragment {
             mVolume = mStorageManager.findVolumeByUuid(fsUuid);
         } else {
             final String volId = getArguments().getString(VolumeInfo.EXTRA_VOLUME_ID);
-            mVolume = mStorageManager.findVolumeById(volId);
+            if (volId != null) {
+                mVolume = mStorageManager.findVolumeById(volId);
+            }
         }
 
         if (!isVolumeValid()) {
@@ -129,6 +131,12 @@ public class PublicVolumeSettings extends SettingsPreferenceFragment {
     @Override
     public void onActivityCreated(Bundle savedInstanceState) {
         super.onActivityCreated(savedInstanceState);
+
+        // If the volume isn't valid, we are not scaffolded to set up a view.
+        if (!isVolumeValid()) {
+            return;
+        }
+
         final Resources resources = getResources();
         final int padding = resources.getDimensionPixelSize(
                 R.dimen.unmount_button_padding);