NPE in RabbitProperties when user is given, but password not

[mhalbritter]

private final RabbitProperties properties = new RabbitProperties();

	@Test
	void determineUsernameWithoutPassword() {
		this.properties.setAddresses("user@rabbit1.example.com:1234/alpha");
		assertThat(this.properties.determineUsername()).isEqualTo("user");
		assertThat(this.properties.determinePassword()).isEqualTo("guest");
	}

This throws an NPE:

java.lang.NullPointerException: Cannot load from object array because "split" is null

	at org.springframework.boot.autoconfigure.amqp.RabbitProperties$Address.parseUsernameAndPassword(RabbitProperties.java:1135)
	at org.springframework.boot.autoconfigure.amqp.RabbitProperties$Address.<init>(RabbitProperties.java:1112)
	at org.springframework.boot.autoconfigure.amqp.RabbitProperties.parseAddresses(RabbitProperties.java:223)
	at org.springframework.boot.autoconfigure.amqp.RabbitProperties.setAddresses(RabbitProperties.java:217)
	at org.springframework.boot.autoconfigure.amqp.RabbitPropertiesTests.determineUsernameWithoutPassword(RabbitPropertiesTests.java:233)
...

The code expects that username and password is given, only username doesn't work.