To reproduce:
1. On http://test.musicbrainz.org/cdstub/puBnSb2Lou_DFuubmKSlxzrRRM0-/import click on "Import CDStub"
2. On the "Release information" tab, click Next
3. On the "Tracklist" tab, click Next
4. On the "Recordings" tab, click Next
5. => Crash

Caught exception in MusicBrainz::Server::Controller::ReleaseEditor::Add->add "Attribute (month) does not pass the type constraint because: Validation failed for 'Int' with value undef at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Edit/Release/Create.pm line 93
MusicBrainz::Server::Edit::Release::Create::build_display_data('MusicBrainz::Server::Edit::Release::Create=HASH(0xd78ae78)', 'HASH(0xd798370)') called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Data/Edit.pm line 477
MusicBrainz::Server::Data::Edit::load_all('MusicBrainz::Server::Data::Edit=HASH(0x81b5290)', 'MusicBrainz::Server::Edit::ReleaseGroup::Create=HASH(0xd7a6cb8)', 'MusicBrainz::Server::Edit::Release::Create=HASH(0xd78ae78)', 'MusicBrainz::Server::Edit::Medium::Create=HASH(0xd6effc0)', 'MusicBrainz::Server::Edit::Medium::AddDiscID=HASH(0xd7b3918)') called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Wizard/ReleaseEditor.pm line 819
MusicBrainz::Server::Wizard::ReleaseEditor::create_common_edits('MusicBrainz::Server::Wizard::ReleaseEditor::Add=HASH(0xaf17f20)', 'edit_note', undef, 'data', 'HASH(0xd6d9850)', 'create_edit', 'CODE(0xd795290)', 'previewing', 1) called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Wizard/ReleaseEditor.pm line 792
MusicBrainz::Server::Wizard::ReleaseEditor::create_edits('MusicBrainz::Server::Wizard::ReleaseEditor::Add=HASH(0xaf17f20)', 'data', 'HASH(0xd6d9850)', 'create_edit', 'CODE(0xd795290)', 'edit_note', undef, 'previewing', 1) called at /home/musicbrainz/perl5/lib/perl5/x86_64-linux-gnu-thread-multi/Moose/Meta/Method/Augmented.pm line 46
MusicBrainz::Server::Wizard::ReleaseEditor::Add::create_edits('MusicBrainz::Server::Wizard::ReleaseEditor::Add=HASH(0xaf17f20)', 'data', 'HASH(0xd6d9850)', 'create_edit', 'CODE(0xd795290)', 'edit_note', undef, 'previewing', 1) called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Wizard/ReleaseEditor.pm line 725
MusicBrainz::Server::Wizard::ReleaseEditor::prepare_edits('MusicBrainz::Server::Wizard::ReleaseEditor::Add=HASH(0xaf17f20)') called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Wizard/ReleaseEditor.pm line 81
MusicBrainz::Server::Wizard::ReleaseEditor::_ANON_ called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Wizard.pm line 163
MusicBrainz::Server::Wizard::navigate_to_page('MusicBrainz::Server::Wizard::ReleaseEditor::Add=HASH(0xaf17f20)') called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Wizard.pm line 379
MusicBrainz::Server::Wizard::_route('MusicBrainz::Server::Wizard::ReleaseEditor::Add=HASH(0xaf17f20)', 'MusicBrainz::Server::Form::ReleaseEditor::Recordings=HASH(0xc...') called at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Wizard.pm line 128