Cryptic error when using service definition with no authentication section defined

[twschiller]

Steps to Reproduce

• Add a service definition without an authentication section (e.g., for a webhook)
• When running the brick that uses the service you'll get an error Cannot read properties of undefined (reading 'config')

Investigation

• For local configs, the error is likely here: http://github.com/pixiebrix/pixiebrix-extension/blob/3b15b511dee8d67510a9f642f598de8df236210f/src/background/requests.ts#L176-L176

Workaround

• Define an empty authentication headers section for the service:

authentication:
  headers: {}