Move IVSGitExt null check to top

Don't initialize this service if IVSGitExt  isn't available.

Author: jcansdale

src/GitHub.TeamFoundation.14/Base/TeamExplorerServiceHolder.cs

@@ -42,17 +42,20 @@ public class TeamExplorerServiceHolder : ITeamExplorerServiceHolder
         /// <param name="joinableTaskFactory">Used for switching to the Main thread.</param>
         public TeamExplorerServiceHolder(IVSGitExt gitService, JoinableTaskContext joinableTaskContext)
         {
+            if (gitService == null)
+            {
+                // This might be null in Blend or SafeMode
+                return;
+            }
+
             JoinableTaskCollection = joinableTaskContext.CreateCollection();
             JoinableTaskCollection.DisplayName = nameof(TeamExplorerServiceHolder);
             JoinableTaskFactory = joinableTaskContext.CreateFactory(JoinableTaskCollection);
 
             this.gitService = gitService;
 
             UpdateActiveRepo();
-            if (gitService != null)
-            {
-                gitService.ActiveRepositoriesChanged += UpdateActiveRepo;
-            }
+            gitService.ActiveRepositoriesChanged += UpdateActiveRepo;
         }
 
         // set by the sections when they get initialized
@@ -151,8 +154,7 @@ void NotifyActiveRepo()
 
         void UpdateActiveRepo()
         {
-            // NOTE: gitService might be null in Blend or Safe Mode
-            var repo = gitService?.ActiveRepositories.FirstOrDefault();
+            var repo = gitService.ActiveRepositories.FirstOrDefault();
 
             if (!Equals(repo, ActiveRepo))
             {