webmap-import: Don't crash when trying to insert a feature without geometry.HEADmaster

Cf. for instance

	$ ogrinfo ./LST.vbk_projekteringsomraden.shp -sql "SELECT * FROM \"LST.vbk_projekteringsomraden\" WHERE OMRID = '1452-V-008'"
        […]
	Layer name: LST.vbk_projekteringsomraden
	Geometry: Polygon
	Feature Count: 1
	Extent: (-907106.000000, 727.000000) - (914131.738200, 7573766.311200)
	Layer SRS WKT:
	PROJCRS["SWEREF99 TM",
        […]
	OGRFeature(LST.vbk_projekteringsomraden):2043
	  OMRID (String) = 1452-V-008
	  PROJNAMN (String) = Grimsås Äspås
	  ANTALVERK (Integer64) = 0
	  AntalejXY (Integer64) = (null)
	  CALPROD (Real) = 0.000000000000000
	  PBYGGSTART (String) = (null)
	  PDRIFT (String) = (null)
	  Andringsan (String) = (null)
	  UnderByggn (String) = (null)
	  ORGNAMN (String) = Kraftö AB
	  ORGNR (String) = 556708-7456
	  EJAKTUELL (String) = Yes
	  KOMNAMN (String) = Tranemo
	  LANSNAMN (String) = Västra Götalands l
	  EL_NAMN (String) = (null)
	  Raderat (String) = No
	  ArendeStat (String) = (null)

0 files changed, 0 insertions, 0 deletions