Calling the project workflow schemes endpoint intermittently results in undefined workflow scheme IDs

Issue Summary

Calling the project workflow schemes endpoint intermittently results in undefined being returned as the workflow scheme ID. This was raised in response to https://community.developer.atlassian.com/t/calling-get-workflow-schemes-api-sometimes-returns-undefined-instead-of-an-id/50328.

Steps to Reproduce

1. Call /rest/api/2/workflowscheme/project
2. Observe the value of values.0.workflowScheme.id

Expected Results

The value at step 2 always identified a valid workflow scheme ID.

Actual Results

The value at step 2 is intermittently undefined. 

Workaround

Call the endpoint again until a valid workflow scheme ID is returned.