Fix in LatticeSequence: when subsequence was last element it wasn't flattened.
Fix in LatticeSequence: when subsequence was last element it wasn't flattened.

EuropeanSpallationSource/openxal,luxiaohan/openxal-csns-luxh,luxiaohan/openxal-csns-luxh,openxal/openxal,openxal/openxal,openxal/openxal,EuropeanSpallationSource/openxal,luxiaohan/openxal-csns-luxh,EuropeanSpallationSource/openxal,EuropeanSpallationSource/openxal,EuropeanSpallationSource/openxal,luxiaohan/openxal-csns-luxh,openxal/openxal,openxal/openxal