Disable background page scrolling when modals are open.

props celloexpressions.
fixes #29074.
Built from https://develop.svn.wordpress.org/trunk@29346


git-svn-id: http://core.svn.wordpress.org/trunk@29124 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Plugin install: Add missing closing HTML tags.

props jwenerd.
fixes #29090. see #28673.
Built from https://develop.svn.wordpress.org/trunk@29348


git-svn-id: http://core.svn.wordpress.org/trunk@29125 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid an undefined index notice in wp_reschedule_event().

props paulschreiber.
fixes #29077.
Built from https://develop.svn.wordpress.org/trunk@29349


git-svn-id: http://core.svn.wordpress.org/trunk@29126 1a063a9b-81f0-0310-95a4-ce76da25c4cd