Exception when trying to register more than one specimen tube for a case

[Nicklas Nordborg]

1. Start the specimen tube registration wizard and enter a case name.
2. In the second step set "Number of tubes" to 2 (or higher). The rest of the information can be left empty or filled in. It doesn't seem to matter.
3. In the third step, boxes should already be filled in. Use the 'Suggest' links to automatically get row and column coordinates or enter them manually.
4. As soon as coordinates for at least two specimen tubes have been entered (or suggested) the form is disabled and an error message is displayed:

For input string: "null"

Currently there seems to be workaround and it is not possible to register cases with more than one specimen tube.