fix: check whether REMOTE_CHARACTER_URLS env is defined in starting agent

[dev-whoan]

Relates to

• Without this condition it will return Unhandled error in startAgents when REMOTE_CHARACTER_URLS is not defined in environment variable

Risks

large

• Agent will not be started.

Background

What does this PR do?

• Fix hasValidRemoteUrls so the agent can be operated.

What kind of change is this?

• Bug fix.
  • To operate agent without REMOTE_CHARACTER_URLS env var, and the function name
    • hasValidRemoteUrls, it should check whether the env has set or not.
    • Without this PR, it will return following error when the env is not set.

    ⛔ ERRORS
    [eliza] Unhandled error in startAgents: 
    {} 
    

Documentation changes needed?

• No.

Testing

• No test. just easy fix.

Where should a reviewer start?

• Only 1 file changed, eliza/agent/index.ts -> hasValidRemoteUrls

Detailed testing steps

Discord username

@Patata