Previously, using a command like
[con_id=foo] kill
would kill the currently focused window because while an error for
not being able to parse the con_id was logged, no further action
was taken, which caused the criterion to be ignored. In this case,
the fallback behavior of using the focused window took over.
For con_id, id and window_type we now reject incorrect values with
an error and abort the command.
fixes#2091
Ingo Bürk