Out of bounds fix when marking an item as read

W/dalvikvm( 2470): threadid=1: thread exiting with uncaught exception (group=0x40a5d1f8)
E/AndroidRuntime( 2470): FATAL EXCEPTION: main
E/AndroidRuntime( 2470): java.lang.IndexOutOfBoundsException: Invalid index 2, size is 2
E/AndroidRuntime( 2470):    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
E/AndroidRuntime( 2470):    at java.util.ArrayList.get(ArrayList.java:304)
E/AndroidRuntime( 2470):    at java.util.Collections$SynchronizedList.get(Collections.java:537)
E/AndroidRuntime( 2470):    at de.danoeh.antennapod.adapter.ExternalEpisodesListAdapter.getChild(ExternalEpisodesListAdapter.java:79)