Adding a Default instance for comparison

Author: StanleyGoldman

src/GitHub.Exports/Models/UsageModel.cs

@@ -5,6 +5,11 @@ namespace GitHub.Models
     [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1815:OverrideEqualsAndOperatorEqualsOnValueTypes", Justification = "It'll use reflection by default and we're fine with that")]
     public struct UsageModel
     {
+        public static UsageModel Default = new UsageModel
+        {
+            Guid = Guid.Empty
+        };
+
         public Guid Guid { get; set; }
         public DateTimeOffset Date { get; set; }
         public string AppVersion { get; set; }

src/GitHub.VisualStudio/Services/UsageTracker.cs

@@ -131,7 +131,7 @@ async Task<UsageModel> GetCurrentReport(UsageData data)
         {
             var current = data.Reports.FirstOrDefault(x => x.Date.Date == DateTimeOffset.Now.Date);
 
-            if (current == null)
+            if (current.Equals(UsageModel.Default))
             {
                 var guid = await service.GetUserGuid();
                 current = UsageModel.Create(guid);