Fails for models with no levels

[MadsHolten]

I have some mechanical IFC models from Aveva that load fine in web-ifc. Since they don't contain levels, however, they do not work with fragments. I am looking through the code and I can see that none of the items are considered unique and hence they are handled by the processMergedItems method on the DataConverter. this._spatialStructure.itemsByFloor[instance.id] returns undefined for all instances, and that seems to create issues further down the line...

Unfortunately, I cannot share the file.