MediaWiki:Default-skin-not-found-no-skins

Whoops! The default skin for your wiki, defined in $wgDefaultSkin as $1, is not available.

You have no installed skins.

If you have just installed or upgraded MediaWiki
You probably installed from git, or directly from the source code using some other method. This is expected. MediaWiki 1.24 and newer doesn't include any skins in the main repository. Try installing some skins from mediawiki.org's skin directory, by:
Doing this should not interfere with your git repository if you're a MediaWiki developer. See Manual: Skin configuration for information how to enable skins and choose the default.