error if map extension isn't valid

src/main.c

@@ -18,6 +18,8 @@ int	main(int argc, char **argv)
 
 	if (argc != 2)
 		return (printf("Usage: ./cub3d mapfile.cub\n"), EXIT_FAILURE);
+	if (ft_strncmp(argv[1] + ft_strlen(argv[1]) - 4, ".cub", 4))
+		return (printf("Wrong map file extension"), EXIT_FAILURE);
 	env = load_map(argv[1]);
 	if (!env)
 		return (EXIT_FAILURE);

src/parsing/getline.c

@@ -40,6 +40,8 @@ char	*get_next_line(const int fd)
 	char		*ret;
 	char		*next;
 
+	if (fd == -1)
+		return (NULL);
 	if (!*buffer)
 		buffer[read(fd, buffer, BUFFER_SIZE)] = 0;
 	ret = ft_calloc(1, sizeof(char));