Ngwpc 11078 11080 subsetting error

[danielcumpton]

[Short description explaining the high-level reason for the pull request]

Additions

If a gage is on a single flowpath with no up or downstream flowpaths, it won't get subset because it's not part of the graph. In this case, the subset can be done using the single flowpath id. Added code to handle the case where the flowpath id is not found in the graph then checking to see if the flowpath exists and if it's standalone. Then subset using just the single flowpath.

Removals

Changes

Testing

Screenshots

Notes

Todos

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Visually tested in supported browsers and devices (see checklist below 👇)
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Testing checklist

Target Environment support

• Windows
• Linux
• Browser

Accessibility

• Keyboard friendly
• Screen reader friendly

Other

• Is useable without CSS
• Is useable without JS
• Flexible from small to large screens
• No linting errors or warnings
• JavaScript tests are passing