Workflows; 'Cannot add zero-length key to collection' error in built-in Workflow Summary Page

Workflow Summary Page may fail with 'Cannot add zero-length key to collection' error.

This can happen in certain circumstances when the Script uses a 'popupnote' HTML templates or other template that uses a pipe character ('|') to separate template content with content containing the equals sign with a space before it, e.g.:

{{popupnote popupnote icon='Note' tooltip='Click to view Notes'| some text =$123}}