Closing proto-repl pane causes error on subsequent attempts to start

[sparkofreason]

If I choose "Close Pane" from the context menu in the proto-repl pane, subsequent attempts to restart just show an empty pane. The following error appears in dev tools:

Uncaught (in promise) Error: The workspace can only contain one instance of item [object Object]
    at ItemRegistry.module.exports.ItemRegistry.addItem (C:\Users\dave\AppData\Local\atom\app-1.20.0\resources\app\src\item-registry.js:11:21)
    at PaneContainer.didAddPaneItem (C:\Users\dave\AppData\Local\atom\app-1.20.0\resources\app\src\pane-container.js:269:29)
    at Pane.module.exports.Pane.addItem (C:\Users\dave\AppData\Local\atom\app-1.20.0\resources\app\src\pane.js:553:22)
    at Pane.module.exports.Pane.activateItem (C:\Users\dave\AppData\Local\atom\app-1.20.0\resources\app\src\pane.js:489:20)
    at Workspace.<anonymous> (C:\Users\dave\AppData\Local\atom\app-1.20.0\resources\app\src\workspace.js:1174:20)
    at Generator.next (<anonymous>)
    at step (C:\Users\dave\AppData\Local\atom\app-1.20.0\resources\app\src\workspace.js:11:279)
    at process._tickCallback (internal/process/next_tick.js:103:7)

Closing the tab works fine. Not sure if this is a problem with proto-repl or Atom.