Not showing files with German “Umlaute”

Hi, there is a bug in the plugin: File manager won’t show any files with names containing letters like “?” “?” “ü” (guess it will be the same for other languages’ special characters, but only can tell for these in German very common characters).

Could you please implement a fix in the next update as I like the plugin very much and it would facilitate my work if I had not to rename all my files.