Duplicate entry '1' in node_gallery_relationship_type upon upgrade

@fugazi reported this problem over in #1863638-3: after upgrade to D7 image is not altered in file_managed. . I'm separating it out for separate tracking.

When running an upgrade, it seems that somehow multiple entries are being generated in the node_gallery_relationship_type table. Node Gallery should be moving over a record for each node gallery relationship that existed in the D6 site, but for some reason it attempts to insert the same relationship multiple times into the table.

The full text of the error is:

WD node_gallery_relationship_type: PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1' for key             [error]

'PRIMARY': INSERT INTO {node_gallery_relationship_type} (id, label, filefield_name, settings) VALUES (:db_insert_placeholder_0,
:db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array
(
    [:db_insert_placeholder_0] => 1
    [:db_insert_placeholder_1] => Node Gallery Default
    [:db_insert_placeholder_2] => field_node_gallery_image
    [:db_insert_placeholder_3] => a:6:{s:12:"relationship";a:1:{s:4:"name";s:20:"Node Gallery
Default";}s:9:"item_view";a:3:{s:17:"display_navigator";i:1;s:27:"view_navigator_item_display";s:39:"node_gallery_gallery_item_views:embed_5";s:13:"pa
ge_fragment";i:0;}s:12:"manage_items";a:6:{s:12:"items_fields";a:20:{s:5:"title";s:5:"title";s:10:"body_field";i:0;s:20:"revision_information";i:0;s:6
:"author";i:0;s:7:"options";i:0;s:16:"comment_settings";i:0;s:4:"path";i:0;s:17:"detailed_question";i:0;s:13:"sexybookmarks";i:0;s:3:"url";i:0;s:11:"c
lick_count";i:0;s:10:"last_click";i:0;s:11:"last_status";i:0;s:16:"last_status_info";i:0;s:12:"last_checked";i:0;s:7:"urlhash";i:0;s:10:"reciprocal";i
:0;s:15:"image_navigator";i:0;s:23:"nopremium_message_field";i:0;s:24:"field_node_gallery_image";i:0;}s:14:"items_per_page";i:20;s:15:"enable_rotation
";b:1;s:15:"rotation_radios";b:1;s:14:"rotation_modal";b:1;s:11:"item_fields";a:1:{s:18:"node_gallery_ref_1";s:18:"node_gallery_ref_1";}}s:2:"og";a:1:
{s:10:"sync_items";b:1;}s:17:"relationship_type";a:2:{s:13:"gallery_types";a:1:{i:0;s:20:"node_gallery_gallery";}s:10:"item_types";a:1:{i:0;s:18:"node
_gallery_image";}}s:10:"view_modes";a:2:{s:4:"full";a:1:{s:4:"view";s:39:"node_gallery_gallery_item_views:embed_1";}s:6:"teaser";a:1:{s:4:"view";s:39:
"node_gallery_gallery_item_views:embed_6";}}}
)
 in drupal_write_record() (line 7106 of K:\xampp\htdocs\fbk1212\includes\common.inc).
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1' for key 'PRIMARY'                                                    [error]

Performed update: node_gallery_update_7002                                                                                                        [ok]