When a vector layer is exported to an OWSContext document, we throw an
exception when the layer contains no features, and the geometries are to be
exported inside of an InlineGeometry-element.
This commit fixes this behaviour by exporting sth. like this in such cases:
<Layer name="vector" hidden="0">i
<ows:Title xmlns:ows="http://www.opengis.net/ows"/>
<InlineGeometry/>
</Layer>
798d2b2cb7