Fix error:
1. no break in cases  wkbMultiPoint, wkbMultiPolygon, wkbMultiLineString so the code in case wkbGeometryCollection executed too.
2. OGRMultiPoint, OGRMultiPolygon, OGRMultiLineString is inherited from OGRGeometryCollection so the code is all the same for all such cases (see: http://www.gdal.org/ogr/classOGRGeometryCollection.html)