Catch UncaughtException when serving in non-Markbind directories

[AgentHagu]

What is the purpose of this pull request?

• Documentation update
• Bug fix
• Feature addition or enhancement
• Code maintenance
• DevOps
• Improve developer experience
• Others, please explain:

Overview of changes:
Fixes #2570

Currently, there is an issue when using the markbind serve command in non-Markbind directories, leading to an UncaughtException that is displayed to the user.

The problem seems to be due to be a missing process.exit() after catching the error. This leads to the code continuing on despite the rootFolder still being undefined.

The PR also updates the error message to be more user-friendly.

Anything you'd like to highlight/discuss:
This PR only fixes the UncaughtException issue, not the underlying issue mentioned in #1825.

Testing instructions:
Try using the markbind serve command in a non-Markbind directory. The UncaughtException should not show. For example:

Proposed commit message: (wrap lines at 72 characters)
Catch UncaughtException when serving in non-Markbind directories

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Checklist: ☑️

• Updated the documentation for feature additions and enhancements
• Added tests for bug fixes or features
• Linked all related issues
• No unrelated changes

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Reviewer checklist:

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Breaking change release note preparation (if applicable):

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[Tim-Siu]

Thanks for the good catch! The process is indeed supposed to exit after catching the error.

[gerteck]

[gerteck]

LGTM! Nice catch! Love the simple fix 👍

[tlylt]

@AgentHagu could we take this opportunity to improve the error message, adding something along the line of "this directory does not appear to contain a MarkBind site"

[lhw-1]

Agreed with @tlylt; the fix itself atm is good to go, but we can include the error message display in this PR as well @AgentHagu

[AgentHagu]

@tlylt @lhw-1 Thanks for the suggestion! As discussed, I will add an extra message after the existing one for better user readability

[AgentHagu]

I've updated the error message to look like this now

[lhw-1]

I'm thinking we can also include suggestions, for beginner friendliness: e.g. "This directory does not appear to contain a valid MarkBind site. Check that you are running the command in the correct directory!"

[AgentHagu]

I'm thinking we can also include suggestions, for beginner friendliness: e.g. "This directory does not appear to contain a valid MarkBind site. Check that you are running the command in the correct directory!"

Sounds good! Will adjust the message accordingly

[AgentHagu]

I have updated the PR to add the suggestions

[lhw-1]

LGTM! A simple but useful fix for those new to MarkBind. Thanks @AgentHagu!

[github-actions]

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[github-actions]

@lhw-1 Each PR must have a SEMVER impact label, please remember to label the PR properly.