♻️ (sum_tail): refactor sum tails to handle empty slice

Author: yuanyu90221

arrays-and-slices/sum.go

@@ -19,8 +19,12 @@ func SumAll(numbersToSum ...[]int) []int {
 func SumAllTails(numbersToSum ...[]int) []int {
 	var sums []int
 	for _, numbers := range numbersToSum {
-		tail := numbers[1:]
-		sums = append(sums, Sum(tail))
+		if len(numbers) == 0 {
+			sums = append(sums, 0)
+		} else {
+			tail := numbers[1:]
+			sums = append(sums, Sum(tail))
+		}
 	}
 	return sums
 }