Reported by @tw4l
Quick fix for the bug I introduced in 1bc3c35 in #2481. I didn't
properly test on the workflow editor in a "new workflow" state, and
didn't realize that the component that fetches the workflow state for an
existing workflow wouldn't be rendered for a new workflow, so the update
to the loading state never occurred for new workflows. This fix
explicitly sets `isCrawlRunning` to `false` instead of `null` for new
workflows, so that the loading state isn't displayed.
Tested locally with both new and existing workflows (in both non-running
and running states).
b471192cbc