Clicking the current document tab shouldn't jump to edit mode

Reproduce:

• Preview a document
• Click the tab of the document that is in preview
• The preview now switches to edit mode

Clicking the tab should keep the document in the mode it is in (either preview or edit), and not switch from preview to edit.

Unwanted side effect of this bug:

• Although the tab switches to edit mode, it doesn't create a Draft, which leads to "No Draft version" errors