If array label is empty, use label of array element

[AntoineChalons]

Currently, for an array of cluster, JKI-EasyXML uses the label of the array, in most cases this is fine for me, but in some cases it's not what I want, therefore my suggestion to improve this is the following :

if the label of the array in an empty string, use the label of the cluster inside the array instead.

And actually this can be generalized to arrays of anything.