ogc:Function

sql like filter:

(  ! (`t`.`the_geom` is null)  or GeometryType(`t`.`the_geom`) = 'POLYGON' )

<ogc:Filter>
  <ogc:Or>
    <ogc:Not>
      <ogc:PropertyIsNull>
        <ogc:PropertyName>the_geom</ogc:PropertyName>
      </ogc:PropertyIsNull>
    </ogc:Not>
    <ogc:PropertyIsEqualTo>
      <ogc:Function name="GeometryType">
        <ogc:PropertyName>the_geom</ogc:PropertyName>
      </ogc:Function>
      <ogc:Literal>POLYGON</ogc:Literal>
    </ogc:PropertyIsEqualTo>
  </ogc:Or>
</ogc:Filter>