Fixing null check

Author: StanleyGoldman

src/GitHub.VisualStudio/Services/UsageTracker.cs

@@ -126,7 +126,7 @@ async Task<UsageModel> GetCurrentReport(UsageData data)
         {
             var current = data.Reports.FirstOrDefault(x => x.Date.Date == DateTimeOffset.Now.Date);
 
-            if (current == null)
+            if (Guid.Empty.Equals(current.Guid))
             {
                 var guid = await service.GetUserGuid();
                 current = UsageModel.Create(guid);