Steps to replicate the issue (include links if applicable):
Go to:
http://localhost:8080/wiki/Special:CreateZObject?view=function-editor
Type first few letters of a new language and select it.
What happens?:
The new language is added but the box doesn't clear of the letters you typed.
What should have happened instead?:
Once you've selected the language the box should reset.
Software version (skip for WMF-hosted wikis like Wikipedia):
Other information (browser name/version, screenshots, etc.):