How to reproduce:

• In the certificate list click the "Open a new tab" button.
• Alternatively, import some certificates to get a new tab with the imported certificates.

Actual result:

• After "Open a new tab" all columns seem to have the default size (100 pixels). (This seems to be caused by an old column layout stored in the configuration. I think the column layout of closed tabs should be removed from the configuration.)
• After importing the columns seem to have been resized to the contents.

Expected result:

• A new tab is shown with the same column layout as the previously shown tab.