Minimal project with `use-management-port` set causes NPE on api-docs endpoint

[dominic-jones]

Describe the bug
In a minimal example, use-management-port is generating NPEs when accessing v3/api-docs.

java.lang.NullPointerException: null
	at org.springdoc.core.ActuatorProvider.getApplicationPort(ActuatorProvider.java:185) ~[springdoc-openapi-common-1.5.2.jar:1.5.2]
	at org.springdoc.api.AbstractOpenApiResource.getActuatorURI(AbstractOpenApiResource.java:1061) ~[springdoc-openapi-common-1.5.2.jar:1.5.2]
	at org.springdoc.webmvc.api.OpenApiActuatorResource.getServerUrl(OpenApiActuatorResource.java:152) ~[springdoc-openapi-webmvc-core-1.5.2.jar:1.5.2]
	at org.springdoc.webmvc.api.OpenApiResource.calculateServerUrl(OpenApiResource.java:295) ~[springdoc-openapi-webmvc-core-1.5.2.jar:1.5.2]
	at org.springdoc.webmvc.api.OpenApiResource.openapiJson(OpenApiResource.java:171) ~[springdoc-openapi-webmvc-core-1.5.2.jar:1.5.2]
	at org.springdoc.webmvc.api.OpenApiActuatorResource.openapiJson(OpenApiActuatorResource.java:131) ~[springdoc-openapi-webmvc-core-1.5.2.jar:1.5.2]

This appears to be because the ActuatorProvider is trying to access a port from a null applicationWebServer. However the previous call's if statement in AbstractOpenApiResource might also be taking the wrong path. It could also be that my example is too minimal and I am missing some configuration.

To Reproduce

• Steps to reproduce the behavior:
• Created a simple project with one api endpoint, no groupings.
• Add Springdoc, v3/api-docs returns valid apis.
• Enable use-management-port, and set a management port.
• actuator/openapi produces NPE

What version of spring-boot you are using?

• 2.4.1
  What modules and versions of springdoc-openapi are you using?
• 1.5.2

Expected behavior

• The same response I get when accessing without using the management port.

[bnasslahsen]

@dominic-jones,

Unfortunately, this issue is not reproducible.
Please add or refer to a sample minimal project in GITHUB, that reproduces this issue.

This ticket is now closed. And can be reopened if a reproducible project is provided.