Bug: File dialog fails to open on MacOS

[JG8203]

Description

In MacOS, attempting to load a SoundFile in Preferences using the Load button or opening a MIDI File, the buttons don't trigger the macOS File Dialog. Instead it does nothing. According to the documentation, a file browser would open allowing the user to select a .sf2 or .sf3 file, or a MIDI file for the File >> Open Dialog. Instead, nothing happens on both cases

Steps to Reproduce

1. Run the PianoBooster application on MacOS (Tahoe, v26.0.1)
2. From the Menu Bar: Setup >> Midi Setup
3. Select the Fluid Synth Tab
4. Click the Load Button
5. No File Dialog Appears

Environment

- OS: MacOS Tahoe, v26.0.1

Related Issue: https://forum.qt.io/topic/162825/qfiledialog-getopenfilename-fails-to-display-dialog-with-native-macos

[JG8203]

Fix: #351