bn_lcm incorrect result with negative zero input

[Guido Vranken]

The following should print 0 but it prints 123.

#include <relic_conf.h>
#include <relic.h>

static void print(const bn_t bn) {
    const size_t size = bn_size_str(bn, 10);
    char* s = malloc(size);
    bn_write_str(s, size, bn, 10);
    printf("%s\n", s);
    free(s);
}

int main(void)
{
    if ( core_init() != RLC_OK ) abort();

    bn_t A, B, R;

    bn_null(A); bn_new(A);
    bn_null(B); bn_new(B);
    bn_null(R); bn_new(R);

    const char* s1 = "123";
    const char* s2 = "-0";

    bn_read_str(A, s1, strlen(s1), 10);
    bn_read_str(B, s2, strlen(s2), 10);

    bn_lcm(R, A, B);

    print(R);

    bn_free(A);
    bn_free(B);
    bn_free(R);
    return 0;
}