Memory: Gracefully return an empty list when sessionId is undefined | null

[Morriz]

Checked

• I searched existing ideas and did not find a similar one
• I added a very descriptive title
• I've clearly described the feature request and motivation for it

Feature request

Please do not throw an error or assume a valid sessionId when provided with sessionId: undefined | null, but instead bootstrap a dummy instance that returns an empty list on each invocation.

The distinction between undefined | null may be used to accommodate backwards compatibility if need be. I don't hope that the memory abstraction currently accepts an emtpy sessionId, but haven't seen any test around that scenario.

Motivation

This so that we may avoid invoking memory for "heavy" callers, such as those providing email bodies. Please do not say that we should do this imperatively, as the world is moving towards declarative idempotent instantiations/wiring (as in no-code solutions).

Proposal (If applicable)

No response