With relation to [SPR-11126] problem converting empty parameter to List,

We want to get a request parameter with the type of List<String> in the Spring-mvc Controller class like below

```java
SampleController.java
@RequestMapping(value = "/urlpath")
public void create(@RequestParam(value = "param") List<String> paramList) {
 ...
}
```

When invoking ".../urlpath?param=", We expect `List<String>` has size 1 with empty String value, but actually the size of `List<String>` is 0.

Actually `StringUtils.commaDelimitedListToStringArray(String)` method is a real worker, but the purpose of that method is to return the empty array in case of empty input(by java doc).
So, I slightly chnaged `convert(Object source, TypeDescriptor sourceType,
TypeDescriptor targetType)` method in the `StringToCollectionConverter`
class.

reated Issue: