[NUI] Add Null check in Slider Dispose

- 'editModeIndicator' of Slider class is not created all the time.
 So, added Null check for this variable.

Signed-off-by: Seoyeon Kim <seoyeon2.kim@samsung.com>

diff --git a/src/Tizen.NUI.Components/Controls/Slider.cs b/src/Tizen.NUI.Components/Controls/Slider.cs
index 92e2be8..b1701f1 100755 (executable)
--- a/src/Tizen.NUI.Components/Controls/Slider.cs
+++ b/src/Tizen.NUI.Components/Controls/Slider.cs
@@ -1651,8 +1651,11 @@ namespace Tizen.NUI.Components
                 this.TouchEvent -= OnTouchEventForTrack;
 
                 recoverIndicator = null;
-                editModeIndicator.Dispose();
-                editModeIndicator = null;
+                if (editModeIndicator != null)
+                {
+                    editModeIndicator.Dispose();
+                    editModeIndicator = null;
+                }
             }
 
             base.Dispose(type);