get_index_string_dim: Fix dimansion report for file = NULL

void get_index_string_dim(feh_file *file, Imlib_Font fn, int *fw, int *fh)

{

	int line_w, line_h;

	char fake_file = 0;

	gib_list *line, *lines;

	static int max_w = 0, total_h = 0;

	if (!opt.index_info)

		return;

	/* called with file = NULL in the setup phase.

	 * We need a fake file, otherwise feh_printf will remove format specifiers,

	 * leading e.g. to a 0x0 report for index_dim = "%n".

	 */

	if (file == NULL) {

		file = feh_file_new("foo");

		file->info = feh_file_info_new();

	}

	line = lines = feh_wrap_string(create_index_string(file), opt.thumb_w * 3, fn, NULL);

	while (line) {

	}

	gib_list_free_and_data(lines);

	printf("dim is %dx%d\n", max_w, total_h);

	if (fake_file)

		feh_file_free(file);

	*fw = max_w;

	*fh = total_h;