Twenty Fifteen: unfix the sidebar if we have a menu with submenus as there is a chance visitors might not be able to scroll down to see submenus in some situations.

Props mattwiebe, fixes #30208.


Built from https://develop.svn.wordpress.org/trunk@30324


git-svn-id: http://core.svn.wordpress.org/trunk@30323 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: cleaning up JS introduced in r30305 that doesn't pass jshint.

Props boonebgorges, fixes #29988.


Built from https://develop.svn.wordpress.org/trunk@30325


git-svn-id: http://core.svn.wordpress.org/trunk@30324 1a063a9b-81f0-0310-95a4-ce76da25c4cd