Trouble adding/editing objects

[Ldp]

Introduced with 2652:

Open a new layer or load an existing .osm, and try to add a node ('a'). Doesn't work. Left toolbar icon also stays at the top one. Existing nodes in the .osm can be moved/deleted, most of the time.

Curiously, adding a node in an existing way mostly works. The virtual nodes disappear though, when finally making it into edit mode on an existing object, through clicking the left toolbar instead of 'a'.

[jttt]

(In [2654]) Fixed #4201 Trouble adding/editing objects