How do I correctly free my arrays without errors?

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I came up with this code with the help of @GWW and now I can't free a char**.

Here's my code (it just reads an input file and prints the names in it on the screen):

    /*   deallocate2D
corresponding function to dynamically deallocate 2-dimensional array using
 * malloc.
 * accepts a char** as the "array" to be allocated, and the number of rows.
 * as with all dynamic memory allocation, failure to free malloc'ed memory
 * will result in memory leaks
 */
void deallocate2D(char** array, int nrows) {

    /*  deallocate each row  */
    int i;
    for (i = 0; i < nrows; i++) {
        free(array[i]);
    }

    /*  deallocate array of pointers  */
    free(array);
}

int readInputFile(FILE *fp, char **file_images) {
    num_lines = 0;
    int s = 10;
    char line[MAX_LENGTH];
    char **final_filenames;

    while (fgets(line, sizeof line, fp) != NULL) /* read a line */ {
        if (line[0] != '\n') {
            if (num_lines >= s) {
                s += 100;
                if ((file_images = (char**) realloc(file_images, s * sizeof (char*))) == NULL) {
                    printf("Error reallocating space for 2d array: %s\n", strerror(errno));
                    return -1;
                }
            }
            if ((file_images[num_lines] = malloc(MAX_LENGTH * sizeof (char))) == NULL) {
                printf("Error allocating space for 2d array: %s\n", strerror(errno));
                return -1;
            }

            strncpy(file_images[num_lines], line, MAX_LENGTH);
            if (file_images[num_lines] == NULL) {
                printf("Strncpy failed: %s\n", strerror(errno));
                return -1;
            }
            printf("name of file %d is: %s \n", num_lines, file_images[num_lines]);
            num_lines++;
        }
    }
    printf("Num_lines: %d\n",num_lines);
    //realloc to number of lines in the file, to avoid wasting memory
    if ((final_filenames = realloc(file_images, num_lines * sizeof (char*))) == NULL) {
        printf("Error reallocating space for 2d array: %s\n", strerror(errno));
        return -1;
    } else {
        file_images = final_filenames;
        deallocate2D(final_filenames, num_lines);
    }
    return 0;
    //don't forget to free lines 2d array! (here or at the end of the code)
}

int main(int argc, char *argv[]) {
    //pixel* image;
    char **images_filenames;

    //check parameters
    if (argc < 4) {
        printf("Incorrect usage.\nPlease use \"./invert input_filename.ppm charWidth charHeight \"\n");
        return -1;
    }

    printf("Opening input file [%s]\n", argv[1]);
    FILE *fpin = fopen(argv[1], "r");
    if (fpin == NULL) {
        printf("Could not open input file\n");
        return -1;
    }
    if ((images_filenames = ((char**) malloc(10 * sizeof (char*)))) == NULL) {
        printf("Error allocating initial space for 2d array: %s\n", strerror(errno));
        return -1;
    }

    if (readInputFile(fpin, images_filenames) == -1) {
        printf("Error reading image filenames from input\n");
        return -1;
    }

    fclose(fpin);
    printf("###########\n");

    deallocate2D(images_filenames, num_lines);

    printf("Done!\n");
    return 0;
}

So, I don't understand why can't I free final_filenames and images_filenames.