can't delete clusters in "expanded" state

[lvavassori]

If deleting a cluster that is in “expanded” state, the cluster remains visible in this state, and when “collapsed”, although it disappears, I get this error message:

ERROR:rendercanvas:Error during handling key_down event
Traceback (most recent call last):
File "/Users/lauravavassori/.local/lib/python3.13/site-packages/rendercanvas/_coreutils.py", line 50, in log_exception
yield
File "/Users/lauravavassori/.local/lib/python3.13/site-packages/pygfx/objects/_events.py", line 395, in handle_event
callback(event)
~~~~~~~~^^^^^^^
File "/Users/lauravavassori/tractome/tractome/app.py", line 696, in handle_key_strokes
self.collapse_streamline_bundles()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "/Users/lauravavassori/tractome/tractome/app.py", line 732, in collapse_streamline_bundles
self._3D_scene.add(self._cluster_reps[bundle.rep])
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
KeyError: np.int32(3618)

After that, the only actions allowed are cluster selection, deselection or expansion (cannot collapse, delete, recluster or go back to previous state). It would be useful to allow removal of expanded clusters as it is more straightforward operationally - you visualise the streamlines and then you remove them.