Better optimize for empty Markdown text fields.
Empty Markdown text fields still had a loading indicator (which was

partly cut off) and ran through all the linkifying and conversion steps.

We no longer show the loading indicators in this case, or do any

processing.

Tested with review requests with empty fields, full fields, and mixed.

Only saw the loading spinners for the fields that had text. Markdown

was properly processed on the fields with text.