Add to project dialog shown while document is already part of project

If a document is already part of a project the application still shows the "Add to project" dialog in the right-side panel. Clicking the "ADD" button does no harm though and everything just works, but of course the dialog should not be displayed.

Reproduction (on enterprise hap of feature branch)

• Open a channel via channel tab  of a project in project perspective
• Click the orange "Edit content" button of a document in the channel manager
• Click "ADD" when Add to project dialog appears.
• make a change and save and close (document is now part of project).
• Click orange "Edit content" button once more for the same document

Expect: Document opens in edit mode without "add to project dialog"
Actual: Add to project dialog is shown

As stated, clicking "ADD" does open the document for editing without any problems.