AHU fails if V_dot_sup is zero
Created by: MichaMans
The AHU fails if the suplly volume flow is zero. We should take care of this. One solution is to set the supply volume flow to a very small parameter (Modelica.Constants.eps) if the supply volume flow is zero. A better option is to check if the model has an equation which can be converted in an equation where V_dot_sup doesn't is the denominator.