No preview Configuration:Changes button in tool bar not displayed if user first discard and again make changes in component property dialog

Steps to reproduce:
Make sure channel preview configuration is not present and if any delete it.

1. enter into channel in edit mode
2. Change one of the parameters in any of the component property dialog.
3. Discard changes
4. Change parameters again in same component property dialog
5. Notice "changes" button in toolbar is not displayed.

Expected:Changes button should be displayed after user discard and change the parameters in component property dialog.