Synfig Animation Studio

Sometimes, using shift+click on a tangent to split it make that error
message appears :
----
value_desc_set: value_node_const_set: value_desc_set: You must be in
Animate-Editing-Mode to directly manipulate this value
----
And the error message pops up again as soon as it's closed, leaving no
choice but a "kill <synfigpid>".

To reproduce the error:
Create a BLine shape, with the default "unsplited" tangents, then animate
one of the node tangents. Go out of the Animation mode, and shift-click on
that tangent, then the message appears and loops forever.