Changing Sequence pattern yields error

[JesusGuerrero]

When testing UI validations, it was noticed that Sequence node was unable to update the sequence pattern that were corrected as part of UI validations.

Steps:

1. open test-union-sequence-nlp.json from the sample flows & load input document
2. Rename Union RevenueByDivision to RevenueDivision, and update the upstream Sequences' attribute to RevenueDivision
3. Run the Union, verify output
4. Open RevenueOfDivision Sequence, attempt to update sequence pattern to match updated Union node name.
5. Error occurs when trying to update sequence. workaround is to discard the sequence node and add a new one.