AssertionError - solvers.CG

Hello,

I updated my NGSolve Environment to 1909 and now I get an AssertionError (# either pre or freedofs must be given) in the solvers.CG method.
Indeed I use my solver without a preconditioner: solvers.CG(mat=a.mat, rhs=res, sol=du, tol=1E-06, maxsteps = 100)

What do I have to change to update to the new behavior?

Thanks for your help in advance!

You need to pass the freedofs of the space. freedofs=fes.FreeDofs(). Actually this was necessary to work savely with dirichlet bcs before was well, we just put the check in for safety.
Best
Christopher