returning peer info should not return {} if the relation doesnt exist

returning {} can cause issues later down the road [see this conversation](https://chat.charmhub.io/charmhub/pl/o467np6z8idd386hqb9icm7fmr)

Start by tracing the operator code that returns peer information and inspect how it handles a missing relation. Use the linked conversation for context about downstream problems, then verify that the behavior for an absent relation is no longer an empty object.

Written by the indexing model from the issue text.