migration-assistant crash if existing partition type changed during install

Binary package hint: ubiquity

Target system has two existing NTFS partitions. The first is supposed to be FAT32 for a future FreeDOS install and the second is WinXP. Test performed with Xubuntu Herd5 liveCD. If I change the first partition to FAT32 during manual partitioning, the migration assistant subsequently fails.

Relevant terminal output is as follows:

Mar 14 04:33:53 ubiquity: Partman: state = [['', None, None]]
Mar 14 04:33:56 ubiquity: Starting up '['log-output', '-t', 'ubiquity', '--pass-stdout', '/usr/lib/ubiquity/migration-assistant/ma-ask', '/usr/lib/ubiquity/migration-assistant']' for ubiquity.components.migrationassistant.MigrationAssistant
Mar 14 04:33:56 ubiquity: Watching for question patterns ^migration-assistant/partitions, ^migration-assistant/.*/users$, ^migration-assistant/.*/items$, ^migration-assistant/.*/user$, ^migration-assistant/.*/password$, ERROR
Mar 14 04:33:59 ubiquity: ['log-output', '-t', 'ubiquity', '--pass-stdout', '/usr/lib/ubiquity/migration-assistant/ma-ask', '/usr/lib/ubiquity/migration-assistant'] exited with code 1
Exception in GTK frontend (invoking crash handler):
Traceback (most recent call last):
  File "/usr/lib/ubiquity/ubiquity/frontend/gtkui.py", line 1432, in watch_debconf_fd_helper
    return callback(source, debconf_condition)
  File "/usr/lib/ubiquity/ubiquity/filteredcommand.py", line 185, in process_input
    self.status = self.wait()
  File "/usr/lib/ubiquity/ubiquity/filteredcommand.py", line 119, in wait
    self.cleanup()
  File "/usr/lib/ubiquity/ubiquity/components/migrationassistant.py", line 136, in cleanup
    items = self.db.get('migration-assistant/' + part + '/' + user + '/items')
  File "/usr/lib/python2.5/site-packages/debconf.py", line 60, in <lambda>
    lambda *args, **kw: self.command(command, *args, **kw))
  File "/usr/lib/python2.5/site-packages/debconf.py", line 96, in command
    raise DebconfError(status, data)
DebconfError: (20, 'Incorrect number of arguments')

Traceback (most recent call last):
  File "/usr/lib/ubiquity/ubiquity/frontend/gtkui.py", line 1432, in watch_debconf_fd_helper
    return callback(source, debconf_condition)
  File "/usr/lib/ubiquity/ubiquity/filteredcommand.py", line 185, in process_input
    self.status = self.wait()
  File "/usr/lib/ubiquity/ubiquity/filteredcommand.py", line 119, in wait
    self.cleanup()
  File "/usr/lib/ubiquity/ubiquity/components/migrationassistant.py", line 136, in cleanup
    items = self.db.get('migration-assistant/' + part + '/' + user + '/items')
  File "/usr/lib/python2.5/site-packages/debconf.py", line 60, in <lambda>
    lambda *args, **kw: self.command(command, *args, **kw))
  File "/usr/lib/python2.5/site-packages/debconf.py", line 96, in command
    raise DebconfError(status, data)
debconf.DebconfError: (20, 'Incorrect number of arguments')