Navigation blocks do not display when quick grading is enabled

There is a mis-matched </div> tag in the function display_submissions (/mod/assignment/lib.php), when quickgrade is enabled.

I'm not entirely sure which one is in the wrong place, but line 1151 (just after the comment '/// Print quickgrade form around the table') is one candidate for removal (this seems to fix it).
The other possibly extra </div> tags are around line 1430 (around the line 'echo $OUTPUT->help_icon('enableemailnotification', 'assignment').'</p></div>';') - removing one of them also seems to fix the problem.