嗨我正在尝试更新 ubuntu 16.04 它显示以下错误
W: The repository 'http://ppa.launchpad.net/n-muench/programs-ppa/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/n-muench/programs-ppa/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
我无法在不修复此错误的情况下安装 filezilla。我已经尝试了所有解决方案，但它给了我同样的错误，请帮助我解决这个错误。