Midi usage prompt only shows when resuming Main activity after plugging in midi device

[maks]

Currently a midi device (eg. midi keyboard controller) needs to be plugged in prior to starting the app in order for the "allow to use midi" dialog prompt to be shown. If a midi controller is plugged in while the app is running, need to leave and resume the Main activity (eg go to app Settings menu and return) for the prompt to be shown.