Send an empty error message after global error is cleared

src/dotnet/commands/dotnet-projectmodel-server/Messengers/GlobalErrorMessenger.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
+using Microsoft.DotNet.ProjectModel.Server.Models;
 
 namespace Microsoft.DotNet.ProjectModel.Server.Messengers
 {
@@ -22,6 +23,16 @@ namespace Microsoft.DotNet.ProjectModel.Server.Messengers
             {
                 send(local.GlobalErrorMessage);
             }
+            else
+            {
+                send(new ErrorMessage
+                {
+                    Message = null,
+                    Path = null,
+                    Line = -1,
+                    Column = -1
+                });
+            }
         }
 
         protected override void SetValue(ProjectSnapshot local, ProjectSnapshot remote)