Add nullability annotations to tests in smoke-test/spring-boot-smoke-test-actuator-custom-security

See gh-47263

smoke-test/spring-boot-smoke-test-actuator-custom-security/build.gradle

@@ -31,3 +31,7 @@ dependencies {
 
 	testRuntimeOnly("org.apache.httpcomponents.client5:httpclient5")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}

smoke-test/spring-boot-smoke-test-actuator-custom-security/src/test/java/smoketest/actuator/customsecurity/SampleActuatorCustomSecurityApplicationTests.java

@@ -52,6 +52,7 @@ class SampleActuatorCustomSecurityApplicationTests extends AbstractSampleActuato
 		ResponseEntity<Map> entity = restTemplate().getForEntity(getPath() + "/foo", Map.class);
 		assertThat(entity.getStatusCode()).isEqualTo(HttpStatus.INTERNAL_SERVER_ERROR);
 		Map<String, Object> body = entity.getBody();
+		assertThat(body).isNotNull();
 		assertThat((String) body.get("message")).contains("Expected exception in controller");
 	}