Handle null connections.

src/VisualStudio/Core/Next/Remote/ServiceHubRemoteHostClient.WorkspaceHost.cs

@@ -39,7 +39,9 @@ private class WorkspaceHost : ForegroundThreadAffinitizedObject, IVisualStudioWo
                 _workspace = workspace;
                 _client = client;
                 _currentSolutionId = workspace.CurrentSolution.Id;
-                _currentConnection = new ReferenceCountedDisposable<Connection>.WeakReference(currentConnection);
+                _currentConnection = currentConnection == null
+                    ? default
+                    : new ReferenceCountedDisposable<Connection>.WeakReference(currentConnection);
             }
 
             public void OnAfterWorkingFolderChange()

src/VisualStudio/Core/Next/Remote/ServiceHubRemoteHostClient.cs

@@ -80,7 +80,10 @@ private static async Task RegisterWorkspaceHostAsync(Workspace workspace, Remote
             // projectTracker is sending events, the workspace host can then use that connection 
             // instead of having to expensively spin up a fresh one.
             var currentConnection = await client.TryCreateConnectionAsync(WellKnownRemoteHostServices.RemoteHostService, CancellationToken.None).ConfigureAwait(false);
-            using (var refCountedConnection = new ReferenceCountedDisposable<Connection>(currentConnection))
+            var refCountedConnection = currentConnection == null
+                ? null
+                : new ReferenceCountedDisposable<Connection>(currentConnection);
+            using (refCountedConnection)
             {
                 var host = new WorkspaceHost(vsWorkspace, client, refCountedConnection);