Error for dimensionless parameters in `load_model`

Hey, I saw that this was also an issue somewhere else in the code. When I want to use a dimensionless parameter I get an error from

def evaluate_string_as_brian2_expression(value_string):
    return eval(value_string, units, vars(brian2))

I saw you fixed it at another spot by checking for its type, but the change to eval(str(value_string), units, vars(brian2)) also works and I'm not sure if there is a reason to prefer another fix.