[Bug] Crash trying to load locally saved queue after removing catalogs on Ampache server

[ztx-lyghters]

Should be self-explanatory, Supersonic will crash trying to load previously saved (local) queue of tracks upon starting. This started happened after I did some re-arrangement of catalogs on Ampache server (I removed some of them in order to split them and added it back as multiple catalogs).

This can be fixed (until next such incident) by removing $HOME/.var/app/io.github.dweymouth.supersonicconfig/supersonic/saved-queue.json.

Here's the stdout of me trying to run Supersonic with saved-queue.json still intact and thus experiencing a crash:

ztx:~ $ flatpak run io.github.dweymouth.supersonic
2024/11/24 14:51:16 Starting supersonic...
2024/11/24 14:51:16 Using config dir: /home/ztx/.var/app/io.github.dweymouth.supersoni
2024/11/24 14:51:16 Using cache dir: /home/ztx/.var/app/io.github.dweymouth.supersonic
2024/11/24 14:51:16 failed to load theme file "": open /home/ztx/.var/app/io.github.dw
2024/11/24 14:51:17 systray error: failed to register: The name org.kde.StatusNotifier
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xc193f6]

goroutine 130 [running]:
github.com/dweymouth/supersonic/backend/mediaprovider.(*Track).Copy(...)
        /run/build/supersonic/backend/mediaprovider/model.go:206
github.com/dweymouth/supersonic/backend.(*playbackEngine).copyTrackSliceToMediaItemSlice(...)
        /run/build/supersonic/backend/playbackengine.go:605
github.com/dweymouth/supersonic/backend.(*playbackEngine).LoadTracks(0xc000346000, {0xc002e40300, 0x7, 0xc001f57900?}, 0x0, 0x0)
        /run/build/supersonic/backend/playbackengine.go:223 +0xd6
github.com/dweymouth/supersonic/backend.(*PlaybackManager).LoadTracks(...)
        /run/build/supersonic/backend/playbackmanager.go:124
github.com/dweymouth/supersonic/backend.(*App).LoadSavedPlayQueue(0xc0002f5888)
        /run/build/supersonic/backend/app.go:380 +0xef
github.com/dweymouth/supersonic/ui.(*MainWindow).RunOnServerConnectedTasks.func1()
        /run/build/supersonic/ui/mainwindow.go:197 +0x1b
created by github.com/dweymouth/supersonic/ui.(*MainWindow).RunOnServerConnectedTasks
in goroutine 93
        /run/build/supersonic/ui/mainwindow.go:196 +0x20d