save msc file with period in name fails to open

In Msc (linux appimage MuseScore-2.1-x86_64), after saving a new score (with some notes) named "test_2.1" and forgot to append ".mscz" at the end of the file name, it cannot be opened anymore. The filename is present in the 'open recent files' list, opening it gives error "unknown file type".

The file is not shown in the "Open File ..." dialog (unknown file extension).

Work-around: in a file manager, rename the file to end with ".mscz", so "test_2.1.mscz" in this case, and open it using "Open file ...' (the original entry in the "recent files" list is of course not valid anymore)

version: 871c8ce, linux appimage MuseScore-2.1-x86_64, running on kUbuntu 16.10 x64.