Why am I getting some random values after the output?

#include <stdio.h>
int main()
{
    int k;
    scanf("%d",&k);
    for(int i=0;i<k;i++)
    {
        char num[10];
        scanf("%s",&num);
        int x = num[0]-'0';
        int sum;
        int y;
        for(int i=0;i<10;i++)
        {
            if(num[i]=='\0')
            {
                y = num[i-1]-'0';
                sum = x+y;
                printf("%d\n",sum);
            }
        }   
    }
    return 0;
}

This program is to obtain the sum of first and last digit of a given number. I am getting some random values after the output. Can anyone please explain me this and how do I eliminate it?enter image description here