fix: not call the snap to get rates if assets are empty

[salimtb]

Explanation

This pull request aims to update the multichainAssetsRatesController so that if the assets list is empty, the Snap call is skipped and execution returns immediately.

References

Changelog

@metamask/assets-controllers

• FIXED: if the assets list is empty, the Snap call is skipped and execution returns immediately.

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

[Prithpal-Sooriya]

nit (happy to ignore since this is a test).
Could we satisfy the type by using the defaultState from the controller? Or is the types quite complex?

const mockNewState = { ...defaultState }
mockNewState.accountAssets = { account: [] }
messenger.publish('MultichainAssetsController:stateChange', mockNewState)