How to fix this code written in C? - c

Question

It works perfectly well for a 20-20 table but for anything else it crashes.
the file is in this link:http://www.csd.uoc.gr/~hy100/glid.txt.
I can not figure out what the problem is because when I put an 20-20 table it works and when
I give a 21-20 table it does the job perfectly fine but crashes before being able to return 0; .
#include <stdio.h>
#include <stdlib.h>
int height, length;
char **world, **new_world;
int load_world_from_file(char filename[]) {
int i, j;
char ch;
FILE *fp;
fp = fopen(filename, "r");
if (fp == NULL ) {
perror("Error while opening the file.\n");
exit(EXIT_FAILURE);
}
fscanf(fp, "%d %d", &height, &length);
printf("here:%d,%d\n", height, length);
/*dilosi dunamika tou pinaka kataxoriseis*/
/* declaration under the table entries */
world = (char **) malloc(sizeof(char *) * (height + 1));/*height + 1 ('\0')*/
for (i = 0; i < 2 * height; i++) {
/* height + height ('|') + 1 ('\0') */
world[i] = (char *) malloc(sizeof(char) * (length + length + 1));
}
/* height + 1 ('\0') */
new_world = (char **) malloc(sizeof(char *) * (height + 1));
for (i = 0; i < 2 * height; i++) {
/* height + height ('|') + 1 ('\0') */
new_world[i] = (char *) malloc(sizeof(char) * (length + length + 1));
}
printf("The contents of %s file are :\n", filename);
i = 0;
j = 0;
while ((ch = fgetc(fp)) != EOF) {
i++;
if (i = length + length + 1) {
j++;
i = 0;
}
world[j] = ch;
printf("%c", world[j]);
}
printf("\n");
for (i = 0; i < (((2 * length) + 2) * height) + 1; i++) {
printf("%c", world[i]);
}
fclose(fp);
return 0;
}
int main() {
char filename[30], filename2[30];
printf("Enter the name of file you want to open:\n");
scanf("%s", &filename);
load_world_from_file(filename);
return 0;
}
Your help is much appreciated.
IT