Can not browse by Movement Label

Unable to browse by Movement Labels because of sql error:

/app/lib/Browse/BrowseEngine.php ~line 3502 adding an array_filter:

$group_by_fields = array_filter(array_unique(array_merge($va_label_order_by_fields, $va_label_ui_fields, ["l.{$vs_label_display_field}", $vs_parent_fld_select, "l.locale_id", "l.{$vs_item_pk}"])));

to remove the empty term returned by $vs_parent_fld_select in line 3500 that causes a sql error

browse.conf:
...
title_facet = {
    type = label,
        restrict_to_types = [],
        preferred_labels_only = 1,

        group_mode = alphabetical,

        label_singular = _("Movement title"),
        label_plural = _("Movement titles")
    },...