fixed crash on empty lines

main.go

@@ -34,6 +34,10 @@ func main() {
 
 	var sum int
 	for _, line := range strings.Split(string(input), "\n") {
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
+
 		var fLine, lLine string
 		for i := 0; i < len(line); i++ {
 			fLine += string(line[i])