Preventing requests to the AnalyticsURL if it is not set

[emahiro]

📑 Summary

I noticed that my self-hosted Mermaid Live Editor is sending requests to the analytics URL when I didn't set the analytics URL and the mermaid domain, and I believe it should be configured according to the instructions provided in the https://github.com/mermaid-js/mermaid-live-editor?tab=readme-ov-file#to-configure-analytics.

My expectation is that the Mermaid Live Editor should not be sending requests to the analytics URL because, according to the README, the default setting is empty, which disables analytics.

Therefore, I would like to make changes to address this issue.

Brief description about the content of your PR:

• Default env value is empty.
• Prevent to request to mermaid.live for analytics if analyticsURL is not set.
• analytics information is better to be empty because of default behavior at README

Resolves #

📏 Design Decisions

Describe the way your implementation works or what design decisions you made if applicable:

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added unit/e2e tests (if appropriate)
• 🔖 targeted develop branch

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