Fix a No href in link warning

For school administrators using GiveCampus Outreach. Controls can differ between the classic email editor and the newer Composer editor.

This validation means the email contains a link element with no destination. The quoted text is the link's visible text; a blank or whitespace-only quote can mean an empty linked space left behind during editing.

In the email editor, inspect the relevant text/button/link, set its intended valid destination or remove the unused link, then preview and revalidate before sending. Do not enter a dummy URL merely to clear validation. If the linked space is difficult to locate in the visual editor, ask support to inspect the saved content. A placeholder-button warning has separate handling and is not the same as a link with no href.