Created attachment 9578 how it looks When 'Show frame' is enabled and there are no entries presently in it, the frame looks like a separator and instead should be hidden.
The option was removed in version 4.15: https://git.xfce.org/xfce/xfce4-panel/commit?id=d77b3b382dd8724489c9210e15f6865964628ba1
Thanks Theo.
Removing this setting would break the Redmond panel profile.
It has already been removed so I suggest you update the profile instead.