Logged in as a tutor to a course with groups of students

Two things
1 All students were included in the table not just the students in this group.
2 The following message preceded the table

Notice: Undefined variable: groupstudents in /var/www/html/icmatest/ou-moodle-dev/mod/quiz/report/overview/overview_table.php on line 45

Warning: implode() [function.implode]: Invalid arguments passed in /var/www/html/icmatest/ou-moodle-dev/mod/quiz/report/overview/overview_table.php on line 45
ERROR: syntax error at or near ")" at character 92

SELECT AVG(qg.grade) AS grade FROM dev_quiz_grades qg WHERE quiz = 132 AND qg.userid IN ( )
? line 796 of lib/dmllib.php: call to debugging()
? line 591 of lib/dmllib.php: call to get_recordset_sql()
? line 48 of mod/quiz/report/overview/overview_table.php: call to get_record_sql()
? line 1242 of lib/tablelib.php: call to quiz_report_overview_table->build_table()
? line 399 of mod/quiz/report/overview/report.php: call to table_sql->out()
? line 94 of mod/quiz/report.php: call to quiz_overview_report->display()

Notice: Trying to get property of non-object in /var/www/html/icmatest/ou-moodle-dev/mod/quiz/report/overview/overview_table.php on line 50

Notice: Trying to get property of non-object in /var/www/html/icmatest/ou-moodle-dev/mod/quiz/report/overview/overview_table.php on line 51