feat(ui): workflow resource check

[psychedelicious]

Summary

These fields are reset back to undefined if not accessible. A warning toast is showing, and in the JS console, the full warning message is logged.

Related Issues / Discussions

n/a

QA Instructions

There are tests for this functionality. To test manually:

• Create a board
• Create a workflow with an image resize node
• Set the board to the new board
• Set an image
• Check the data tab in the bottom left panel of the workflow editor and check that the value for the board and image are populated
• Save the workflow
• Delete the board and image
• Refresh the page
• Re-load the workflow
• Check the data tab in bottom left panel of the workflow editor and check that the value for the board and image are now undefined

Then do the same thing, but with the model loader. You'll need to delete the model between the reloads.

Merge Plan

n/a

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• Documentation added / updated (if applicable)