add class constraint

RaceLapTimer/Interfaces/IPluginLocator.cs

@@ -5,7 +5,7 @@ namespace Interfaces
 {
     public interface IPluginLocator
     {
-        Task<List<T>> LocateAsync<T>();
-        List<T> Locate<T>();
+        Task<List<T>> LocateAsync<T>() where T : class;
+        List<T> Locate<T>() where T : class;
     }
 }

RaceLapTimer/RaceLapTimer/Extensions/PluginLocator.cs

@@ -21,12 +21,12 @@ namespace RaceLapTimer.Extensions
             _logger = logger;
         }
 
-        public async Task<List<T>> LocateAsync<T>()
+        public async Task<List<T>> LocateAsync<T>() where T:class
         {
             return await Task.Run(() => Locate<T>());
         }
 
-        public List<T> Locate<T>()
+        public List<T> Locate<T>() where T:class
         {
             try
             {