Fixed some of the compiler warnings.

Chat/Groups/ChatterGroupManager.cs

@@ -73,7 +73,7 @@ namespace TwitchChatTTS.Chat.Groups
         {
             var values = groupNames.Select(g => _groups.TryGetValue(g, out var group) ? group : null).Where(g => g != null);
             if (values.Any())
-                return values.Max(g => g.Priority);
+                return values.Max(g => g!.Priority);
             return 0;
         }