ERROR: null value in column "attemptnumber" violates not-null constraint

INSERT INTO assign_grades (assignment,userid,timecreated,timemodified,grade,grader,attemptnumber) VALUES($1,$2,$3,$4,$5,$6,$7) RETURNING id

[array (

   'assignment' => '590',

   'userid' => '223',

   'timecreated' => 1392977454,

   'timemodified' => 1392977454,

   'grade' => -1,

   'grader' => '2',

   'attemptnumber' => NULL,

)]

dmlwriteexception

line 444 of /lib/dml/moodle_database.php: dml_write_exception thrown

line 239 of /lib/dml/pgsql_native_moodle_database.php: call to moodle_database->query_end()

line 848 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->query_end()

line 900 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->insert_record_raw()

line 2660 of /mod/assign/locallib.php: call to pgsql_native_moodle_database->insert_record()

line 588 of /mod/assign/feedback/editpdf/classes/document_services.php: call to assign->get_user_grade()

line 66 of /mod/assign/feedback/editpdf/locallib.php: call to assignfeedback_editpdf\document_services::get_feedback_document()

line 225 of /mod/assign/feedback/editpdf/locallib.php: call to assign_feedback_editpdf->get_widget()

line 205 of /mod/assign/feedback/editpdf/locallib.php: call to assign_feedback_editpdf->view()

line 1097 of /mod/assign/gradingtable.php: call to assign_feedback_editpdf->view_summary()

line 1206 of /mod/assign/gradingtable.php: call to assign_grading_table->format_plugin_summary_with_link()

line 729 of /lib/tablelib.php: call to assign_grading_table->other_cols()

line 433 of /mod/assign/gradingtable.php: call to flexible_table->format_row()

line 1330 of /lib/tablelib.php: call to assign_grading_table->format_row()

line 1442 of /lib/tablelib.php: call to table_sql->build_table()

line 1185 of /mod/assign/renderer.php: call to table_sql->out()

line 981 of /mod/assign/renderer.php: call to mod_assign_renderer->flexible_table()

line 221 of /lib/outputrenderers.php: call to mod_assign_renderer->render_assign_grading_table()

line 3068 of /mod/assign/locallib.php: call to plugin_renderer_base->render()

line 3107 of /mod/assign/locallib.php: call to assign->view_grading_table()

line 505 of /mod/assign/locallib.php: call to assign->view_grading_page()

line 53 of /mod/assign/view.php: call to assign->view()