[Simulator] Multiple simulation values for channels of same origin clutter the graphical output.
Usually, only one (or few) channel(s) leaving a port have a non-empty
name in order to avoid readability issues in the diagram.
However, during simulation each channel displays the simulation value,
so the readability issue occurs here.
=>
Only show simulation value for channels with non-empty name.
(from redmine: issue id 2875, created on 2017-03-13, closed on 2018-03-06)