How to modify smartfilterbar filters?

Question

I have defined a smart filter bar like the following:

<smartFilterBar:SmartFilterBar id="smartFilterBar" entitySet="DamageReportSet" persistencyKey="SmartFilter_Explored" initialized="onFilterInit">
    <!-- layout data used to make the table growing but the filter bar fixed -->
    <smartFilterBar:layoutData>
        <FlexItemData shrinkFactor="0"/>
    </smartFilterBar:layoutData>
    <smartFilterBar:controlConfiguration>
        <smartFilterBar:ControlConfiguration key="Id" visibleInAdvancedArea="true" preventInitialDataFetchInValueHelpDialog="true" index="1"/>
        <smartFilterBar:ControlConfiguration key="Plant" visibleInAdvancedArea="true" preventInitialDataFetchInValueHelpDialog="true" index="2" id="plantFilterBox">
            <smartFilterBar:defaultFilterValues>
                <smartFilterBar:SelectOption low="{appView>/Role/Plantid}"></smartFilterBar:SelectOption>
            </smartFilterBar:defaultFilterValues>
        </smartFilterBar:ControlConfiguration>      
</smartFilterBar:SmartFilterBar>

In some cases the {appView>/Role/Plantid} property is empty. Now the question is how can I modify the smart filter bar and remove the default value or the filter when it is empty!?.

Actually when it is empty it will apply a filter for empty values!

I tried something like this but was not the answer:

onFilterInit: function(oEvent){
    this.byId("plantFilterBox").destroyDefaultFilterValues();
    oEvent.getSource().clearVariantSelection();
}