Fixed: Handle missing category when getting Qbittorrent download path

Fixes LIDARR-24B
Fixes LIDARR-2PM
Fixes LIDARR-55T

(cherry picked from commit 6f97ca9a55471386454457ca52b93733e18e85e4)

Co-authored-by: ta264 <ta264@users.noreply.github.com>

src/NzbDrone.Core/Download/Clients/QBittorrent/QBittorrent.cs

@@ -366,9 +366,7 @@ namespace NzbDrone.Core.Download.Clients.QBittorrent
 
             if (Settings.MusicCategory.IsNotNullOrWhiteSpace() && version >= Version.Parse("2.0"))
             {
-                var label = Proxy.GetLabels(Settings)[Settings.MusicCategory];
-
-                if (label.SavePath.IsNotNullOrWhiteSpace())
+                if (Proxy.GetLabels(Settings).TryGetValue(Settings.MusicCategory, out var label) && label.SavePath.IsNotNullOrWhiteSpace())
                 {
                     var labelDir = new OsPath(label.SavePath);