Ensure that entries in a list of lists are not lost during sanitization

Closes gh-8263
See gh-8197

Author: izeye

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/ConfigurationPropertiesReportEndpoint.java

@@ -259,10 +259,9 @@ private List<Object> sanitize(String prefix, List<Object> list) {
 				sanitized.add(sanitize(prefix, (Map<String, Object>) item));
 			}
 			else if (item instanceof List) {
-				sanitize(prefix, (List<Object>) item);
+				sanitized.add(sanitize(prefix, (List<Object>) item));
 			}
 			else {
-				item = this.sanitizer.sanitize(prefix, item);
 				sanitized.add(this.sanitizer.sanitize(prefix, item));
 			}
 		}