[Maduk86]

Description

Please explain the changes you made here.
Emissions.get_cloud_geo_region() returned the state column whenever it was not None. impact.csv is loaded with pandas, so an empty state cell is NaN, not None, and NaN was returned instead of falling back to city. This affects 30 of the 40 GCP regions (e.g. asia-east1). Changed the check to isinstance(state, str).

Related Issue

Please link to the issue this PR resolves: [issue - Fixes #1456]

Motivation and Context

Why is this change required? What problem does it solve?
For cloud regions without a state, region was empty in emissions.csv, HTTPOutput failed on the NaN value, and LoggerOutput wrote invalid JSON.

How Has This Been Tested?

Please describe in detail how you tested your changes.
Added two tests in tests/test_emissions.py:

• test_get_cloud_geo_region_returns_state: gcp/us-central1 returns "Iowa"
• test_get_cloud_geo_region_falls_back_to_city_without_state: gcp/asia-east1 returns "Changhua County" (fails before the fix with nan != 'Changhua County')

Ran uv run task test-package locally; all tests pass.

Screenshots (if appropriate):

Types of changes

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• [x ] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

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Go over all the following points, and put an x in all the boxes that apply.

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• [x ] I have read the docs/how-to/contributing.md document.
• [x ] I have added tests to cover my changes.
• [x ] All new and existing tests passed.

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