Element: Work around jQuery bug with empty strings in `addClass()`
Element: Work around jQuery bug with empty strings in `addClass()`

Bug: T298737
Change-Id: I444c34f2c03c90f507ee7feffdc2e6e375da936a

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui