Fix error in table_connector, that resulted in the node not being activated
when clicking on a row of the table. The error was subtly introduced when
adding an extra column before the target treenode ID column.
Fixed improper call of staticSelectNode.
Must always provide a skeletonID as second argument, even if null
for a connector node.
Refactored code out of send_to_fragments_group to create _fragments_group_id function.