Editor adds unneeded extra line below panel

Issue descriptions

Using page layout with header section, columns and footer section.
Putting a panel in the header adds an unneeded empty line below the
panel. This line can be removed by deleting in the editor.
After the save the page looks good.
However if a user afterwards just opens page in the editor and saves it
the empty line will be added again.
This is annoying!

Steps to reproduce

#Create a page, add a info box in the "header cell" and remove the empty line below. Save.
#Showing the correct rendering.
#Opening the page in the new editor. The empty line appears again below the info box. Now just save...
#Showing the now existing empty line.

Screenshot