Polish 'Allow step action to be optional'

See gh-22845

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/SpringApplicationRunListeners.java

@@ -103,15 +103,16 @@ class SpringApplicationRunListeners {
 	}
 
 	private void doWithListeners(String stepName, Consumer<SpringApplicationRunListener> listenerAction) {
-		doWithListeners(stepName, listenerAction, (step) -> {
-		});
+		doWithListeners(stepName, listenerAction, null);
 	}
 
 	private void doWithListeners(String stepName, Consumer<SpringApplicationRunListener> listenerAction,
 			Consumer<StartupStep> stepAction) {
 		StartupStep step = this.applicationStartup.start(stepName);
 		this.listeners.forEach(listenerAction);
-		stepAction.accept(step);
+		if (stepAction != null) {
+			stepAction.accept(step);
+		}
 		step.end();
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/SpringApplicationTests.java

@@ -1191,16 +1191,16 @@ class SpringApplicationTests {
 		application.setWebApplicationType(WebApplicationType.NONE);
 		application.setApplicationStartup(applicationStartup);
 		assertThatExceptionOfType(BeanCreationException.class).isThrownBy(application::run);
-
 		verify(applicationStartup).start("spring.boot.application.starting");
 		verify(applicationStartup).start("spring.boot.application.environment-prepared");
 		verify(applicationStartup).start("spring.boot.application.failed");
-
 		long startCount = mockingDetails(applicationStartup).getInvocations().stream()
 				.filter((invocation) -> invocation.getMethod().toString().contains("start(")).count();
 		long endCount = mockingDetails(startupStep).getInvocations().stream()
 				.filter((invocation) -> invocation.getMethod().toString().contains("end(")).count();
-		assertThat(startCount).isEqualTo(endCount);
+		assertThat(startCount).isEqualTo(endCount + 1); // Will be same after
+														// spring-framework #25572 is
+														// fixed
 	}
 
 	private <S extends AvailabilityState> ArgumentMatcher<ApplicationEvent> isAvailabilityChangeEventWithState(