MediaInfoFragment: avoid a crash accessing the Activity

YOU SHALL NOT call getActivity before onActivityCreated() in a fragment

And of course, update() was called in onCreateView

vlc-android/src/org/videolan/vlc/gui/video/MediaInfoFragment.java

@@ -79,11 +79,15 @@ public class MediaInfoFragment extends ListFragment {
         mAdapter = new MediaInfoAdapter(getActivity());
         setListAdapter(mAdapter);
 
-        update();
-
         return v;
     }
 
+    @Override
+    public void onActivityCreated(Bundle savedInstanceState) {
+        super.onActivityCreated(savedInstanceState);
+        update();
+    }
+
     public void setMediaLocation(String MRL) {
         if (MRL == null)
             return;