Copying and renaming a Custom Theme is asking user to Save changes

Having a previously created Custom Theme (Graphite):

• User navigates to Designer > Themes
• Hovering over "Graphite" theme, click on Copy - User is taken to a copy of the Custom Theme (Graphite_copy), not yet saved.
• User changes the theme's name to "Graphite_2" - This theme appears in the the sidebar, under Themes, at the same time a "You need to save or discard your latest changes." message appears.
  
• If the user Saves the changes, there will be both a "Graphite_2" and a "Graphite_copy" in the Themes list, which shouldn't happen since the renaming was done to the copy that was being created.

Probably related to this issue, if the user renames the "Graphite_2" theme and saves the changes, all the Custom Themes mentioned in this issue disappear from the Themes list, although they appear in the Resources tab.