When a new debugger is shown, the implementation of
attempts to add a new tab to a JTabbedPane by counting the components in the tabbed pane, and adding the new tab to 'index minus one'.
The amount of components in a JTabbedPane need not be equal to the amount of tabs in the pane, which can cause
to be thrown.
When adding a new tab 'to the end' of the pane, the index
can (should?) be used as a shortcut to get the correct index.