<RadGrid> Grouping only more than one item

[Maciej]

Hello.
I have a problem. I'm trying to achive one thing ( as I wrote in a title ), but what I have is hard to get rid of.
Data source is gotten from a database as a list via linq. I set up groupin by expression tags

<GroupByExpressions>
    <telerik:GridGroupByExpression>
        <SelectFields>
            <telerik:GridGroupByField FieldAlias="Gmina" FieldName="NazwaOrganuProwadzacego"
                FormatString="{0:D}" />
        </SelectFields>
        <GroupByFields>
            <telerik:GridGroupByField FieldName="NazwaOrganuProwadzacego" SortOrder="Ascending" />
        </GroupByFields>
    </telerik:GridGroupByExpression>
    <telerik:GridGroupByExpression>
        <SelectFields>
            <telerik:GridGroupByField FieldAlias="Nazwa Placówki" FieldName="NazwaPlacowki" FormatString="{0:D}" />
        </SelectFields>
        <GroupByFields>
            <telerik:GridGroupByField FieldName="NazwaPlacowki" SortOrder="Ascending" />
        </GroupByFields>
    </telerik:GridGroupByExpression>
</GroupByExpressions>

And it is groupped but it's too much for me.
I made a picture of a simple table that represents of how it looks like ( "is.png" ), and how I want it to look like ( "want.png" ).

Thanks in advance for every kind of help.
Maciej.

[Maciej]

Does exist a statement in telerik library: if( volume != null ) then add to group ?