fix: issue with the biggest group calculus

I've known about this one for almost a year.
Feels good to finally get around to it.

models/poll_tally.go

@@ -96,19 +96,24 @@ func (pct *PollCandidateTally) GetBiggestGroup(aroundGrade uint8) (groupSize int
 
 	for k, _ := range pct.Poll.GetGradationList() {
 		grade := uint8(k)
-		//for _, grade := range pct.Poll.GetGrades() {
+		gradeAmount := int(pct.Grades[grade].Amount)
+
+		if 0 == gradeAmount {
+			continue
+		}
 		if grade < aroundGrade {
-			belowGroupSize += int(pct.Grades[grade].Amount)
+			belowGroupSize += gradeAmount
 			belowGroupGrade = grade
 		}
 		if grade > aroundGrade {
-			aboveGroupSize += int(pct.Grades[grade].Amount)
+			aboveGroupSize += gradeAmount
 			if 0 == aboveGroupGrade {
 				aboveGroupGrade = grade
 			}
 		}
 	}
 
+	// /!. Assumption of LOW median with `>` /!.
 	if aboveGroupSize > belowGroupSize {
 		return aboveGroupSize, aboveGroupSign, aboveGroupGrade
 	}