Update Solution.java

Author: ThanhNIT

src/main/java/g3001_3100/s3099_harshad_number/Solution.java

@@ -12,7 +12,7 @@ public int sumOfTheDigitsOfHarshadNumber(int x) {
             sum = sum + digit;
             temp = temp / 10;
         }
-        if (x % sum == 0) {
+        if (sum !=0 && x % sum == 0) {
             return sum;
         }
         return -1;