CS50 pset3 Plurality: why does vote function not return false when given invalid candidate?

Question

According to check50, the vote function does not return false when given a name of an invalid candidate. Furthermore, it modifies total votes when voting for an invalid candidate. I left the main function unchanged, according to instructions. Please help? What am I not seeing here?

Edit: added the rest of the code. When I run it with the example Alice and Bob as candidates and try to vote for Steve, instead of "Invalid vote" as the output should be, it gives me "Segmentation fault".

#include <cs50.h>
#include <stdio.h>
#include <string.h>

// Max number of candidates
#define MAX 9

// Candidates have name and vote count
typedef struct
{
    string name;
    int votes;
}
candidate;

// Array of candidates
candidate candidates[MAX];

// Number of candidates
int candidate_count;

// Function prototypes
bool vote(string name);
void print_winner(void);

int main(int argc, string argv[])
{
    // Check for invalid usage
    if (argc < 2)
    {
        printf("Usage: plurality [candidate ...]\n");
        return 1;
    }

    // Populate array of candidates
    candidate_count = argc - 1;
    if (candidate_count > MAX)
    {
        printf("Maximum number of candidates is %i\n", MAX);
        return 2;
    }
    for (int i = 0; i < candidate_count; i++)
    {
        candidates[i].name = argv[i + 1];
        candidates[i].votes = 0;
    }

    int voter_count = get_int("Number of voters: ");

    // Loop over all voters
    for (int i = 0; i < voter_count; i++)
    {
        string name = get_string("Vote: ");

        // Check for invalid vote
        if (!vote(name))
        {
            printf("Invalid vote.\n");
        }
    }

    // Display winner of election
    print_winner();
}

// Update vote totals given a new vote
bool vote(string name)
{
    for (int i = 0; i < MAX; i++)
    {
        if (strcmp(candidates[i].name, name) == 0)
        {
            candidates[i].votes++;
            return true;
        }
    }
    return false;
}

// Print the winner (or winners) of the election
void print_winner(void)
{
    int high = 0;
    for (int i = 0; i < MAX; i++)
    {
        if (candidates[i].votes > high)
        {
            high = candidates[i].votes;
        }
    }
    for (int j = 0; j < MAX; j++)
    {
        if (candidates[j].votes == high)
        {
            printf("%s\n", candidates[j].name);
        }
    }
    return;
}

Answer 1

In vote and print_winner you loop on entire candidates array.

for (int i = 0; i < MAX; i++)

What do you think can happen when you fill only 2 candidates and try to access 3rd item of array which has not been initialized? Usually, undefined behavior.