Styling issue on IPE cancel button

The "Cancel" button shows as per attached image while performing a series of actions when customizing a page.

Steps
Edit a panel page using the IPE
Add a bit of custom content to the page
Save changes made in page
Edit the page again using the IPR
click on the delete button for the element that you added
Accept alert asking with the following text "Remove this pane?"
click on the "Cancel" button in the black block located at the bottom of the screen
click "Cancel" on the alert that comes up with the following text "This will discard all unsaved changes. Are you sure?"

Expected outcome
the styling of the "cancel" button should not change

Actual outcome
the styling in the "cancel" button breaks with icon-save.png being repeated in the background of the button.