Export retains .mid in the file name erroneously
When "Export..." is selected for, e.g. "MySong.mscz", the export dialog box shows "MySong". If PDF is to be exported, for example, ".pdf" is added automatically to the exported file name.
When a MIDI is exported, the export dialog box shows just "MySong", but the exported file name will be "MySong.mid". The ".mid" does not show in the export dialog box as the file name at this stage.
When a different file type, e.g., ".mxl" is to be exported right after MIDI, however, the dialog box this time shows "MySong.mid". When the Save is clicked, therefore, a pop-up dialog box comes up, asking whether Cancel, Keep ".mid" or change it to ".mxl".
This happens only after MIDI has been exported and another type is to be exported subsequently.
This is reproducible.
OS: macOS High Sierra (10.13), Arch.: x86_64, MuseScore version (64-bit): 220.127.116.112126096, revision: 465e7b6