Bugfix: fixes typo date -> grade_date

src/canvaslms/cli/results.nw

@@ -275,7 +275,7 @@ def summarize_assignment_groups(canvas, args):
 If a student hasn't done anything, the grade and date will be [[None]].
 There is no point in including this in the result.
 <<check if we should skip based on [[grade]]>>=
-if grade is None or date is None:
+if grade is None or grade_date is None:
   continue
 @