Fix optional MXBean test guard

Return early when a platform MXBean is absent so present MXBeans are still validated.

Author: mercyblitz

microsphere-java-core/src/test/java/io/microsphere/management/JmxUtilsTest.java

@@ -357,7 +357,7 @@ void testMethodSignature() {
     }
 
     private void assertPlatformMXBean(Optional<? extends PlatformManagedObject> platformMXBean, String name) throws Throwable {
-        if (platformMXBean.isPresent()) {
+        if (platformMXBean.isEmpty()) {
             return;
         }
         assertPlatformMXBean(platformMXBean.get(), name);