BIAA:
There are special rules for when more or less every councillor has an "interest" in things like that. Plus the legal officers don't always agree with each other (eg a joint district/county committee on which different members receive different legal advice as to the import of their membership of a cycling campaign).
Anyway, full council meetings are a total farce, the motion was harmless and would have been passed unanimously whether I'd voted or not, and I do speak up for GA where it really matters (ie in committee) when appropriate.