Debug an error yielded when no python.analysis.extraPaths item in .vscode/settings.json

[nabenabe0928]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context.
List any dependencies that are required for this change.

This PR relates to a warning yielded during an installation process.
The installation process finishes with an error when we do not have python.analysis.extraPaths in .vscode/settings.json, but this is unwanted, so I fixed this issue.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

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