Issue with core and perimeter zoning of GeoJSON features with narrow segments

[kflemin]

when model is made with narrow segments (see attached model), It comes out in OSM like this missing the core zone:

Assuming that the core and perimeter zoning code in the code geojson gem maybe just can't handle a situation when the resulting core isn't a single polygon. Or maybe this is failing for different reason? If there isn't already a test of similar GeoJSON you could add this one.

*Widening the narrow sections of the model fixes the issue.
in 1.osm.txt