Enable empty node

[pradeeban]

In DHGWorkflow, we can have an empty node such as "OUT:" However, this cannot be created in concore-editor. It throws an error, "Node with incorrect label" when the second part of the label is left empty. This should be allowed, as an "Empty node."

See the . This node naming should be allowed.

[Rahuljagwani]

I have solved this issue , just merging the previous issue #61 pull request will solve this issue also.

[pradeeban]

Thanks a lot, @Rahuljagwani. This is fixed now in main with your contribution.