Prevent error "Notice: Undefined index: idx" if there are no list items are selected.
Prevent error "Notice: Undefined index: idx" if there are no list items are selected.

osavchenko/SonataAdminBundle,Armstrong1992/SonataAdminBundle,peter-gribanov/SonataAdminBundle,osavchenko/SonataAdminBundle,osavchenko/SonataAdminBundle,peter-gribanov/SonataAdminBundle,peter-gribanov/SonataAdminBundle,Armstrong1992/SonataAdminBundle,sonata-project/SonataAdminBundle,osavchenko/SonataAdminBundle,osavchenko/SonataAdminBundle,sonata-project/SonataAdminBundle,peter-gribanov/SonataAdminBundle