Wrong working directory when MuseScore is launched via a file association under Windows

Under Windows, when MuseScore is launched via a file association (e.g., when the user double-clicks a score in File Explorer), MuseScore starts up with the working directory set to that of the opened score instead of the MuseScore application directory.

This has the unfortunate consequence of keeping the directory locked, preventing the user from deleting or renaming it. Because MuseScore never changes the working directory during a session (even if the user closes the score and/or opens a score in a different directory), the only way to delete or rename the directory is to close MuseScore.

When MuseScore is launched normally, it starts up with the working directory set to the application directory. It should always start up that way, no matter how it is launched.

This problem was originally reported here.