Protect against NPE when escaping LiveBeansView

Issue: SPR-12252

Author: philwebb

spring-context/src/main/java/org/springframework/context/support/LiveBeansView.java

@@ -220,6 +220,9 @@ protected boolean isBeanEligible(String beanName, BeanDefinition bd, Configurabl
 	 */
 	protected String getEscapedResourceDescription(BeanDefinition bd) {
 		String resourceDescription = bd.getResourceDescription();
+		if (resourceDescription == null) {
+			return null;
+		}
 		StringBuilder result = new StringBuilder(resourceDescription.length() + 16);
 		for (int i = 0; i < resourceDescription.length(); i++) {
 			char character = resourceDescription.charAt(i);