Fix deleting providers

(cherry picked from commit a6f8391f40b38daba7208db4e2354ceeba4d08fe)

src/Lidarr.Api.V1/ProviderControllerBase.cs

@@ -102,9 +102,10 @@ namespace Lidarr.Api.V1
         }
 
         [RestDeleteById]
-        public void DeleteProvider(int id)
+        public object DeleteProvider(int id)
         {
             _providerFactory.Delete(id);
+            return new object();
         }
 
         [HttpGet("schema")]