title: TFS Solution Explorer missing checkout icon
body: <p>I recently upgraded <code>TFS server</code> from <strong>2013</strong> to <strong>2018.2</strong></p>
  
  <p>Developer with VS2013 can't check-out file from Solution Explorer, but this developer can check-out the same file from Source Control Explorer.
  What is the reason and how to fix?</p>
  
  <p>Log window: Value cannot be null. Parameter name: workspace</p>
  
  <p>Thanks</p>