Interactive form redirect on completion not functioning

Problem/Motivation

When completing an interactive form the page doesn't redirect and instead states

Interactive Task Execution
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Steps to reproduce

Create an interactive form task and handler that submits to complete the task
Set it to have a redirect, or use the default /tasconsole redirect
On submit you get error instead of redirection

Proposed resolution

It appears that on line 108 of the interactive form base the Form is set to rebuild, but that overrides any of the redirects set earlier.

I think the solution is to check for redirects there, it appears to fix it.
Not sure if it should explicitly check for FALSE since it could be NULL or FALSE

    if(!$form_state->getRedirect()) {
      // Rebuild the form if no redirect is set.
      $form_state->setRebuild(TRUE);
    }

It appears to be present from the 2.0 rewrite to the current 4.x branch