Debugging WL for WRF simulation 4 degree case

[claalmve]

Description of PR

Currently, the warming_levels.ipynb notebook is breaking due to the fact that are no WRF simulations that reach 4 degrees warming (a small win for the world). This PR addresses this bug by creating conditional statements for if/when there are no simulations that reach a certain degree of warming.

Summary of changes and related issue We want to still use warming levels and warming levels visualizations even if no simulations reach a certain degree of warming.

Relevant motivation and context We want our notebooks to run properly.

Dependencies required for this change?

Fixes # (issue), delete if not necessary

Type of change

• [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 not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Ran through warming_levels.ipynb

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules