Use default storage instead of the last storage

This pull request is a correction proposal for a bad behavior when the phone doesn't have a SD card.

The navigator.getDeviceStorages return all possible storages, included not available storages. (see https://developer.mozilla.org/en-US/docs/Web/API/DeviceStorage.available)

The navigator.getDeviceStorage return the default storage (internal storage or sd card depending user settings).

The pull request include a finest permision for the app : "music" instead of "sdcard".