don't assert that CGLIB must be present unless there is at least one @Configuration class found

org.springframework.context/src/main/java/org/springframework/context/annotation/support/ConfigurationClassPostProcessor.java

@@ -143,6 +143,10 @@ public class ConfigurationClassPostProcessor extends AbstractConfigurationClassP
 
 		BeanDefinitionRegistry configBeanDefs = getConfigurationBeanDefinitions(true);
 
+		if (configBeanDefs.getBeanDefinitionCount() == 0)
+			// nothing to enhance -> return immediately
+			return;
+
 		assertCglibIsPresent(configBeanDefs);
 
 		ConfigurationEnhancer enhancer = new ConfigurationEnhancer(beanFactory);