reverting changes of #81, hence they cause a freeze of the navigator gui
Revert "Merge branch 'bug/#81-npe-insert-meta-tree-node' into dev"

This reverts commit 80fd132cf6c6a9d32284f2c588789f58ee00727c, reversing
changes made to b66251f56dc7e773c2d62e69eadcb1e28d3b55cb.