[Java] Bouncy Castle AES-CTR null pointer exception

bc.java

Security.addProvider(new BouncyCastleProvider());
Cipher c = Cipher.getInstance("AES/CTR/NoPadding",new BouncyCastleProvider());
System.out.println(c.getProvider());
KeyGenerator kg = KeyGenerator.getInstance("AES");
c.init(Cipher.ENCRYPT_MODE, kg.generateKey());
System.out.println(c.update(new byte[20]).length); // output: 16
System.out.println(c.update(new byte[1]).length);  // null pointer exception