prune records from the SelectionModel if they were selected at the time they were removed.
function(store, records, indexes, isMove) {
        var me = this;

        // If the selection start point is among records being removed, we no longer have a selection start point.
        if (me.selectionStart && Ext.Array.contains(records, me.selectionStart)) {
            me.selectionStart = null;
        }

        if (isMove || me.locked || !me.pruneRemoved) {
            return;
        }
        me.deselectDeletedRecords(records);
    }