Jupgrade [migrating undefined]

The last week or so I've been working on updating and migrating a Joomla! site. Going from Joomla! 1.5.26 to 2.5 seemed to be smart upgrade. Unfortunately I ran into some problems when trying to use Jupgrade to migrate the database. I also got some problems with some outdated components but I got most of the stuff working.
The biggest problem I encountered was the "migrating undefined" problem. Luckily I found an easy, but perhaps ugly, solution to this problem.

Before we go to the steps needed to make the migration work I would like to add just one thing: Backup your database and Backup the site files.  You might actually need the backups.

OK! Let's move on.

The reason that Jupgrade threw this message at me was the fact that the database was removed during the migration script.
I simply went to the installation page in the <web-host>/jupgrade/ -folder and completed the installation.
I made sure to use the same prefix for the database in the installation process as I did when setting the options in the Jupgrade component.

As soon as I was done with the installation; Jupgrade would start migrating my database. I also removed the install -directory from the subfolder named /jupgrade/.

When that was done the big work of moving and updating my template started. (And I'm still working on it.) Now the site is up and running Joomla! 2.5, and I will continue fixing my templates, image-galleries and file-gallery.