Error while restoring backup into a new course

Got the following error while restoring a backup into a new course. lol @ "Will be implemented before 2.0 release"

Error writing to database

More information about this error
Debug info: Column 'userid' cannot be null
INSERT INTO mdl_grade_grades (userid,rawgrade,rawgrademax,rawgrademin,rawscaleid,usermodified,finalgrade,hidden,locked,locktime,exported,overridden,excluded,feedback,feedbackformat,information,informationformat,timecreated,timemodified,itemid) VALUES(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)
[array (
0 => NULL,
1 => NULL,
2 => '100.00000',
3 => '0.00000',
4 => NULL,
5 => NULL,
6 => NULL,
7 => '0',
8 => '0',
9 => '0',
10 => '0',
11 => '0',
12 => '0',
13 => NULL,
14 => '0',
15 => NULL,
16 => '0',
17 => NULL,
18 => NULL,
19 => '17',
)]
Error code: dmlwriteexception
Stack trace:

line 416 of /lib/dml/moodle_database.php: dml_write_exception thrown
line 952 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->query_end()
line 994 of /lib/dml/mysqli_native_moodle_database.php: call to mysqli_native_moodle_database->insert_record_raw()
line 222 of /backup/moodle2/restore_stepslib.php: call to mysqli_native_moodle_database->insert_record()
line 131 of /backup/util/plan/restore_structure_step.class.php: call to restore_gradebook_structure_step->process_grade_grade()
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 146 of /backup/util/plan/base_plan.class.php: call to base_task->execute()
line 157 of /backup/util/plan/restore_plan.class.php: call to base_plan->execute()
line 315 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()

Output buffer: <div class="notifytiny">Skipping 'database' enrolment plugin. Will be implemented before 2.0 release<ul style="text-align: left"><li>line 1496 of /backup/moodle2/restore_stepslib.php: call to debugging()</li><li>line 131 of /backup/util/plan/restore_structure_step.class.php: call to restore_enrolments_structure_step->process_enrol()</li><li>line 103 of /backup/util/helper/restore_structure_parser_processor.class.php: call to restore_structure_step->process()</li><li>line 125 of /backup/util/xml/parser/processors/grouped_parser_processor.class.php: call to restore_structure_parser_processor->dispatch_chunk()</li><li>line 91 of /backup/util/helper/restore_structure_parser_processor.class.php: call to grouped_parser_processor->postprocess_chunk()</li><li>line 148 of /backup/util/xml/parser/processors/simplified_parser_processor.class.php: call to restore_structure_parser_processor->postprocess_chunk()</li><li>line 92 of /backup/util/xml/parser/processors/progressive_parser_processor.class.php: call to simplified_parser_processor->process_chunk()</li><li>line 169 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser_processor->receive_chunk()</li><li>line 253 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser->publish()</li><li>line ? of unknownfile: call to progressive_parser->end_tag()</li><li>line 158 of /backup/util/xml/parser/progressive_parser.class.php: call to xml_parse()</li><li>line 137 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser->parse()</li><li>line 105 of /backup/util/plan/restore_structure_step.class.php: call to progressive_parser->process()</li><li>line 153 of /backup/util/plan/base_task.class.php: call to restore_structure_step->execute()</li><li>line 146 of /backup/util/plan/base_plan.class.php: call to base_task->execute()</li><li>line 157 of /backup/util/plan/restore_plan.class.php: call to base_plan->execute()</li><li>line 315 of /backup/controller/restore_controller.class.php: call to restore_plan->execute()</li><li>line 147 of /backup/util/ui/restore_ui.class.php: call to restore_controller->execute_plan()</li><li>line 46 of /backup/restore.php: call to restore_ui->execute()</li></ul></div>