Clearing resource cache after adding a new store results in a NPE

This is due to a code interaction:

• the web page tries to grab the store from the resource pool before an id is assigned to it to check the configuration is actually working before saving it
• resource pool keyes the store cache by id, which in this case is null
• on cleanup CatalogImpl.getStore(id, ...) is called, and the latter cannot handle null ids

Options:

• we key the store cache by the info object instead of by its id like the other caches
• we don't store in the cache stores whose info id is null
• we make the catalog tolerant to null ids

I would go for the first or the second. What do you think?