Update with a message when the version can't be read

Or otherwise is just the default 0.0.0.0

Author: keveleigh

Assets/MRTK/Core/Inspectors/Setup/MRTKVersionPopup.cs

@@ -10,10 +10,14 @@ namespace Microsoft.MixedReality.Toolkit.Editor
 {
     internal class MRTKVersionPopup : EditorWindow
     {
-        private static MRTKVersionPopup window;
+        private const string DefaultVersion = "0.0.0.0";
+        private const string NotFoundMessage = "The version could not be read. This is most often due to (and expected when) using MRTK directly from the repo. If you're using an official distribution and seeing this message, please file a GitHub issue!";
         private static readonly Version MRTKVersion = typeof(MixedRealityToolkit).Assembly.GetName().Version;
-        private static readonly Vector2 WindowSize = new Vector2(300, 150);
+        private static readonly bool FoundVersion = MRTKVersion.ToString() != DefaultVersion;
+        private static readonly Vector2 WindowSize = new Vector2(300, 140);
+        private static readonly Vector2 NotFoundWindowSize = new Vector2(300, 175);
         private static readonly GUIContent Title = new GUIContent("Mixed Reality Toolkit");
+        private static MRTKVersionPopup window;
 
         [MenuItem("Mixed Reality/Toolkit/Show version...", priority = int.MaxValue)]
         private static void Init()
@@ -26,8 +30,8 @@ private static void Init()
 
             window = CreateInstance<MRTKVersionPopup>();
             window.titleContent = Title;
-            window.maxSize = WindowSize;
-            window.minSize = WindowSize;
+            window.maxSize = FoundVersion ? WindowSize : NotFoundWindowSize;
+            window.minSize = FoundVersion ? WindowSize : NotFoundWindowSize;
             window.ShowUtility();
         }
 
@@ -40,7 +44,7 @@ private void OnGUI()
                 using (new EditorGUILayout.HorizontalScope())
                 {
                     GUILayout.FlexibleSpace();
-                    EditorGUILayout.LabelField($"Version {MRTKVersion}", EditorStyles.wordWrappedLabel);
+                    EditorGUILayout.LabelField(FoundVersion ? $"Version {MRTKVersion}" : NotFoundMessage, EditorStyles.wordWrappedLabel);
                     GUILayout.FlexibleSpace();
                 }
             }