Issue 3408: Console panel breaks if Firebug is reactivated

Steps to reproduce

  1. Open Firebug
  2. Enable and switch to the Console panel
  3. Click on the Execute Test button above
    There should be a log This is a test log in the console
  4. Deactivate Firebug for the site by clicking the close button
  5. Activate Firebug again by clicking the Start Button
  6. Click on the Execute Test button again

Expected result