Edit actions are not updated on the locked sequence detaching in Chromatogram View

Scenario to reproduce:

1. Open "data/samples/ABIF/A01.abi".
2. Call context menu on the chromatogram view, select {Edit new sequence}

   menu item. Accept the dialog.
   Expected state: a new sequence is added to the project.

3. Lock the new document for editing.
4. Call context menu on the chromatogram view, select {Remove edited sequence}

   menu item.
   Expected state: the sequence is removed, actions in the context menu are updated.
   Current state: actions in context menu suppose that the sequence is still attached.