C: Strange behaviour with strtok() - c

Question

I'm doing an exercice where I need to split a string into an array of strings. The number of delimiters is checked before (the code snippet posted is a stripped down version however it doesn't work too), then the string is transformed into lowercase and it gets split into 4 parts separated by the delimiter "-". Here's the code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#define MAX_USERNAME_LENGHT 256
#define NUMBER_OF_ELEMENTS 4
void StringToArrayOfStrings(char *string, char **string_array, char *delimiter);
void LowerString(char * string, int string_lenght);
int main() {
char string[MAX_USERNAME_LENGHT] = "Joseph-Lucy-Mike-Nick"; //Test string
char *string_array[NUMBER_OF_ELEMENTS]; //We need four elements
char delimiter[] = "-";
int counter = 0;
//LowerString(string, strlen(string));
//printf("%s", string);
StringToArrayOfStrings(string, string_array, delimiter);
//Print each element of the string array
for (counter = 0; counter < NUMBER_OF_ELEMENTS; counter++) {
printf("\n%s\n", string_array[counter]);
}
return 0;
}
void LowerString(char * string, int string_lenght) {
unsigned short int counter;
for (counter = 0; counter < string_lenght; counter++) {
string[counter] = tolower(string[counter]);
}
}
void StringToArrayOfStrings(char *string, char **string_array, char *delimiter) {
unsigned short int counter;
char *token;
token = strtok(string, delimiter);
while(token != NULL) {
string_array[counter++] = token;
token = strtok(NULL, delimiter);
}
}
I've been scratching my head for the past 2 hours and I wasn't able to fix it. This programs works only if the string is not printed or/and transformed in lowercase. The program crashes when entering the loop in StringToArrayOfStrings. Where's the problem?
Thanks.