[Coverity 1666155] Use after free in input/item.c

This could cause an immediate crash or incorrect values might be read subsequently resulting in incorrect computations.

In input_item_SetEpg: A pointer to freed memory is dereferenced, used as a function argument, or otherwise used (CWE-416)

 862    if( pp_epg )
 863    {
       7. freed_arg: vlc_epg_Delete frees *pp_epg.[show details]
 864        vlc_epg_Delete( *pp_epg );
      
CID 1666155: (#1 of 1): Use after free (USE_AFTER_FREE)
8. use_after_free: Using freed pointer *pp_epg.
 865        if( *pp_epg == p_item->p_epg_table ) /* current table can have changed */
 866            p_item->p_epg_table = NULL;
 867        *pp_epg = p_epg;
 868    }