Fix return zero size array with empty String parameter in StringUtils.delimiitedListToStringArray

Prior to this commit, zero size String array returns if StringUtils.delimitedListToStringArray is called with parameter empty String ("")

I think, after call StringUtils.delimitedListToStringArray("", ",", null);

it should return one size String array -> [""]

but it returns zero size String array.

StringUtils.delimitedListToStringArray(null, ",", null) & StringUtils.delimitedListToStringArray("", ",", null)

should returns differently. However there are same results.

There's no logic for empty String(""), but just is for null parameter.

I added if statement for "" parameter. The result will be one size String array.

And also in SPR-11126, the issue will be fine.

Issue: SPR-11126