On line 1396 and 1398 same action get_current_group($course->id) is run.

1395 /// Check to see if groups are being used in this course
1396 $currentgroup = get_current_group($course->id);
1397
1398 if ($currentgroup = get_current_group($course->id) && groupmode($course) != 0) {

Possibly replace 1398 with
if ($currentgroup && groupmode($course) != 0) {