Merge pull request #5691 from izeye/prefix

* pr/5691:
  Polish

spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/properties/AnnotationsPropertySource.java

@@ -116,7 +116,6 @@ public class AnnotationsPropertySource extends EnumerablePropertySource<Class<?>
 	}
 
 	private String dotAppend(String prefix, String postfix) {
-		prefix = (prefix == null ? "" : prefix);
 		if (StringUtils.hasText(prefix)) {
 			return (prefix.endsWith(".") ? prefix + postfix : prefix + "." + postfix);
 		}