Debug info: Column 'answerid' cannot be null

INSERT INTO mdl_lesson_attempts (userid,retry,correct,useranswer,timeseen,lessonid,pageid,answerid) VALUES(?,?,?,?,?,?,?,?)

[array (

0 => '5',

1 => '0',

2 => '0',

3 => 'O:8:"stdClass":5:{s:4:"sent";i:0;s:6:"graded";i:0;s:5:"score";i:0;s:6:"answer";s:9:"sadsadsad";s:8:"response";s:0:"";}',

4 => 1331524772,

5 => 5,

6 => 7,

7 => NULL,

)]

Stack trace:

    line 413 of /lib/dml/moodle_database.php: dml_write_exception thrown

    line 901 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->query_end()

    line 943 of /lib/dml/mysqli_native_moodle_database.php: call to mysqli_native_moodle_database->insert_record_raw()

    line 122 of /mod/lesson/backup/moodle2/restore_lesson_stepslib.php: call to mysqli_native_moodle_database->insert_record()

    line 131 of /backup/util/plan/restore_structure_step.class.php: call to restore_lesson_activity_structure_step->process_lesson_attempt()

    line 103 of /backup/util/helper/restore_structure_parser_processor.class.php: call to restore_structure_step->process()

    line 125 of /backup/util/xml/parser/processors/grouped_parser_processor.class.php: call to restore_structure_parser_processor->dispatch_chunk()

    line 91 of /backup/util/helper/restore_structure_parser_processor.class.php: call to grouped_parser_processor->postprocess_chunk()

    line 148 of /backup/util/xml/parser/processors/simplified_parser_processor.class.php: call to restore_structure_parser_processor->postprocess_chunk()

    line 92 of /backup/util/xml/parser/processors/progressive_parser_processor.class.php: call to simplified_parser_processor->process_chunk()

    line 169 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser_processor->receive_chunk()

    line 253 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser->publish()

    line ? of unknownfile: call to progressive_parser->end_tag()

    line 158 of /backup/util/xml/parser/progressive_parser.class.php: call to xml_parse()

    line 137 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser->parse()

    line 105 of /backup/util/plan/restore_structure_step.class.php: call to progressive_parser->process()

    line 153 of /backup/util/plan/base_task.class.php: call to restore_structure_step->execute()

    line 192 of /backup/moodle2/restore_activity_task.class.php: call to base_task->execute()

    line 148 of /backup/util/plan/base_plan.class.php: call to restore_activity_task->execute()

    line 157 of /backup/util/plan/restore_plan.class.php: call to base_plan->execute()

    line 310 of /backup/controller/restore_controller.class.php: call to restore_plan->execute()

    line 147 of /backup/util/ui/restore_ui.class.php: call to restore_controller->execute_plan()

    line 46 of /backup/restore.php: call to restore_ui->execute()