Merge pull request #28 from coryleach/dev

NRE Fix on Exit

Author: coryleach

README.md

@@ -22,15 +22,15 @@ Includes a SRP shader for blurring the background of UI panels.
 #### Using UnityPackageManager (for Unity 2019.3 or later)
 Open the package manager window (menu: Window > Package Manager)<br/>
 Select "Add package from git URL...", fill in the pop-up with the following link:<br/>
-https://github.com/coryleach/UnityGUI.git#3.0.11<br/>
+https://github.com/coryleach/UnityGUI.git#3.0.12<br/>
 
 #### Using UnityPackageManager (for Unity 2019.1 or later)
 
 Find the manifest.json file in the Packages folder of your project and edit it to look like this:
 ```js
 {
   "dependencies": {
-    "com.gameframe.gui": "https://github.com/coryleach/UnityGUI.git#3.0.11",
+    "com.gameframe.gui": "https://github.com/coryleach/UnityGUI.git#3.0.12",
     ...
   },
 }

Runtime/Tween/TweenExtensions.cs

@@ -13,7 +13,7 @@ public static class TweenExtensions
 
         private static CancellationToken CancellationToken => (_cancellationTokenSource != null) ? _cancellationTokenSource.Token : CancellationToken.None;
 
-        private static bool CanTween => CanTweenPredicate.Invoke();
+        private static bool CanTween => CanTweenPredicate.Invoke() && _tweenDict != null;
 
         private static Func<bool> _canTweenPredicate = DefaultCanTweenPredicate;
         public static Func<bool> CanTweenPredicate

package.json

@@ -1,7 +1,7 @@
 {
   "name": "com.gameframe.gui",
   "displayName": "Gameframe.GUI",
-  "version": "3.0.11",
+  "version": "3.0.12",
   "description": "This is a library of GUI helpers for UGUI  \r\nIncludes a panel system that implements a navigation stack.  \r\nIncludes a scene transition system.  \r\nIncludes a SRP shader for blurring the background of UI panels.",
   "keywords": [],
   "author": {