imports wrong on at least some partial exports

[alinsavix]

When exporting world/wmo/brokenisles/eredar/7er_colosseum.wmo with only the "ring" WMO Group enabled, some textures are wrong, probably due to an index getting confused somewhere. Imported with Kru's importer, the textures are right, so presumably this is a problem with WoWbjectImporter.

One of the tower tops, from an import of the full export:

...and one of the tower tops, from an import of just the "ring" group:

Probably low priority, unless it turns out someone really uses the partial export feature of wow.export a bunch.