Map fails to load on wards with a sub-ward

It makes a request for `66A.geojson` when only `66.geojson` exists. Need to alter the URL to just be the ward; not the subward. Or split out the geojson files to actually reflect which divisions are in the each sub-ward.

No file or test is named; start by locating the map request that constructs the 66A.geojson URL. Confirm how ward and sub-ward identifiers are obtained, then make the map request use the ward-only file and verify that a ward with a sub-ward loads successfully.

Written by the indexing model from the issue text.