Panel Wizard Page Layout

Hi!

i use the version XWiki Enterprise 1.8.17790.
i have got to change the Page layout, i selected my favorite layout and pressed the save button.
but I get the following error message:

Rico is not defined
1Failed to load source for sourceFile top-level http://myHost/xwiki/bin/admin/XWiki/XWikiPreferences?&forceLeftPanels=1&forceRightPanels=1&section=Panels.PanelWizard
script.tags( X| 12052 12053 12054 12055 12056 12543 12545 12546 )

In the file: prototype.js
Linie: 4019
Object:
$continue => ""throw $continue" is deprecated, use "return" instead"
Stack: "Error("\"throw $continue\" is deprecated, use \"return\" instead")@:0\n@http://myHost/xwiki/resources/js/prototype/prototype.js:4019\n"

i don't know, where is the problem?

thanks for every tip!
sami