The addition of uls-p-lang-dummy to language_urls makes a broken language button appear on all pages including special pages. On mobile a language section is only shown if languages are available. This has been surfaced by a recent upstream of code we performed to make the mobile skin more compatible with default skins.
This is a hack and should be removed.
I can add another hack to mobile to counter this but I'd rather fix this issue at source if possible...