Empty lines, visible on page or in WYSIWYG text, are created only if you enable them as explained in Insert blank lines.

To delete an empty line, while on page or in WYSIWYG, or in source pane with tags hidden

Just press the BACKSPACE key.

To delete an empty line, while in source pane with tags displayed

Locate the related paragraph containing only the >f F< line and delete all its content.