Describe the bug
When adding a new logical structure element, the new logical element gets selected. But the element which was selected when the structure was added stays selected as well.

This leads to the problem, that the selectable metadata is not derived from the newly added logical node, but from the previously selected node.

One can now add metadata, which does not belong to the newly added node at all and validation does not complain.

In order to get the correct metadata selection, we have to explicitely select the new logical element again.

To Reproduce
Steps to reproduce the behavior:

1. Add a new logical structure element
2. Immediatly click on the Add metadata button
3. The metadata selection gives the options for the previous selected node, not the new inserted node

Expected behavior
When adding a new node the metadata selection should be immediatly restricted down to the newly added node.

Release
3.7, Master