Previously, if security.ignored was set to none and the error controller
was disabled, there would be no paths to ignore and we would call
IgnoredRequestConfigurer.antMatchers with an empty array. While a bit
pointless, this had no effect on Spring Security’s configuration.

This behaviour has changed in the latest 4.0.3 snapshots [1]. An empty
array passed to IgnoredRequestConfigurer.antMatchers now maps to /**. As
Spring Boot configures its ignored paths with highest precedence this
means that security is now disabled for every path.

This commit updates both the management security and application
security configuration to avoid calling antMatchers with an empty
array, thereby ensuring that we don’t inadvertently ignore every path.
Even if the change to Spring Security is reverted we can keep this
change. The behaviour will remain the same and, arguably, it makes the
intent of our configuration clearer.

Closes gh-4345

[1] https://github.com/spring-projects/spring-security/commit/8663ac41731ead18c549a24c2c94b78ce0cceb1b