Why does this code segfault?

[qqsszz]

I'm trying to make a program that separates two values in a string

#include <stdio.h>

void separarUrlYPalabra(char *buff, char *url, char *palabra) {
    int esUrl = 1;
    int contador = 0;
    int largoUrl = 0;
    while(1) {
        printf("%d\n", contador);
        if(*(url+contador) != '{') {
            if(esUrl) {
                *(url+contador) = *(buff+contador);
                contador++;
            }
            else {
                if(*(buff+contador) == '0')
                    return;
                *(palabra+contador-largoUrl) = *(buff+contador);
                contador++;
            }
        }
        else {
            if(*(buff+contador+1) == '}'){
                largoUrl = contador + 2;
                contador = contador + 2;
                esUrl = 0;
            }
            else {
                *(url+contador) = *(buff+contador);
                contador++;
            }
        }
    }
}

int main() {
//delimiter {}
//0 is to know the end of the word
    char buffer[1000] = "https://cboard.cprogramming.com/newthread.php?do=postthread&f=4{}word0";
    char palabra[21];
    char url[90];
    separarUrlYPalabra(buffer, url, palabra);
    printf("%s\n%s\n", url, palabra);
}

[john.c]

void separate(const char *line, char *url, char *word) {
    while (*line) {
        if (*line == '{' && *(line+1) == '}') {
            line += 2;
            while (*line && *line != '0')
                *word++ = *line++;
            *word = '\0';
            break;
        }
        *url++ = *line++;
    }
    *url = '\0';
}

[qqsszz]

man that is a well polished code. I have a question, when will line become NULL so while(*line) is false?

[john.c]

when will line become NULL so while(*line) is false?

line won't become NULL, but it will eventually point to the '\0' character at the end of the string, so *line will be 0 (i.e., false).