Consistent use of Collection.toArray with zero-sized array argument

Includes consistent use of ClassUtils.toClassArray (as non-null variant)

Issue: SPR-16523

spring-oxm/src/main/java/org/springframework/oxm/jaxb/ClassPathJaxb2TypeScanner.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -94,7 +94,7 @@ class ClassPathJaxb2TypeScanner {
 					}
 				}
 			}
-			return jaxb2Classes.toArray(new Class<?>[jaxb2Classes.size()]);
+			return ClassUtils.toClassArray(jaxb2Classes);
 		}
 		catch (IOException ex) {
 			throw new UncategorizedMappingException("Failed to scan classpath for unlisted classes", ex);