Inconsistent behaviour for no initial condition

[Alex-Vasile]

For vector variables, the way to say no initial conditions is to specify them as None in the ic_config.

If the same thing is done with scalar variables (e.g. with concentration for one of the components for MCINS) the simulation will not work properly and produces incorrect results. It appears like the velocity field does not properly convect the components.

When the GridFunction is initialized it is created with 0s everywhere, so it would be expected that None and 0 would produce the same results. At the very least, it would be expected that using None does not break the coupling between the concentration and the velocity field.