[NUI] Fix svace issue (#735)

Signed-off-by: huiyu.eun <huiyu.eun@samsung.com>

diff --git a/src/Tizen.NUI/src/internal/XamlBinding/ObservableWrapper.cs b/src/Tizen.NUI/src/internal/XamlBinding/ObservableWrapper.cs
index b897657..2a220ea 100755 (executable)
--- a/src/Tizen.NUI/src/internal/XamlBinding/ObservableWrapper.cs
+++ b/src/Tizen.NUI/src/internal/XamlBinding/ObservableWrapper.cs
@@ -139,7 +139,7 @@ namespace Tizen.NUI.Binding
                 throw new NotSupportedException("The collection is read-only");
             int innerIndex = ToInnerIndex(index);
             TTrack item = _list[innerIndex];
-            if (item.Owned)
+            if (item != null && item.Owned)
             {
                 _list.RemoveAt(innerIndex);
                 item.Owned = false;