Allow adding to clipboard after copying from new workspace

Steps to reproduce:

• Navigate to a folder containing several documents.
• Select some documents.
• Click on the Add to Clipboard icon.
  => The number of documents added to clipboard appears as a badge on the clipboard icon in the left menu.
• Navigate to Workspaces.
• Create a new workspace.
• Click on the Clipboard icon in the left menu.
• Click on the COPY button.
  => The documents are copied from the clipboard to the new Workspace. The clipboard is now empty.
• Click on the first document in the Workspace.
  => User is taken to the document's view page.
• Click on the Add to Clipboard icon from the document actions.
  => The document is not added to the clipboard.
  => The 1 badge does not appear on the clipboard icon in the left menu.
  => Error in console browser (Chrome):

  elements.html:51806 Uncaught TypeError: Cannot read property 'contains' of undefined
      at HTMLElement.toggle (elements.html:51806)
      at HTMLDivElement.handler (nuxeo-app.html:2291)
      at Object._fire (nuxeo-app.html:7220)
      at Object.forward (nuxeo-app.html:7615)
      at Object.click (nuxeo-app.html:7578)
      at HTMLDivElement._handleNative (nuxeo-app.html:6998)
  toggle	@	elements.html:51806
  handler	@	nuxeo-app.html:2291
  _fire	@	nuxeo-app.html:7220
  forward	@	nuxeo-app.html:7615
  click	@	nuxeo-app.html:7578
  _handleNative	@	nuxeo-app.html:6998
  

  => Error in console browser (Firefox):

  TypeError: this.clipboard is undefined data: Polymer({ is: 'nuxeo-clipboard-toggle-button', :53:9
  toggle
  https://nightly.nuxeo.com/nuxeo/ui/elements.html-164.js:53:9
  handler
  https://nightly.nuxeo.com/nuxeo/ui/nuxeo-app.html-12.js:79:28
  _fire
  https://nightly.nuxeo.com/nuxeo/ui/nuxeo-app.html-17.js:674:7
  forward
  https://nightly.nuxeo.com/nuxeo/ui/nuxeo-app.html-17.js:1069:11
  click
  https://nightly.nuxeo.com/nuxeo/ui/nuxeo-app.html-17.js:1032:9
  _handleNative
  https://nightly.nuxeo.com/nuxeo/ui/nuxeo-app.html-17.js:452:18
  

Workaround:

• Refreshing the page does not add the document to the clipboard, but after a refresh, the user can add the document to the clipboard again, and it seems to work this second time.
• Workaround not possible in Edge because of NXP-25961.