Warning : Invalid argument supplied for foreach() dans node_ds_search_execute() ligne 488

I can't get the DS search module working.
Core search is working normally.
When I enabled Display Suite Search mode instead of regular node search mode I get the following warning :

Warning : Invalid argument supplied for foreach() in node_ds_search_execute() (line 488 in ../ds/modules/ds_search/ds_search.module).

and no more search result is displayed.