characterization of plus fraction fails when mole fraction of a component is 0

[Even Solbraa]

Describe the bug
characterization of plus fraction fails when mole fraction of a component is 0

Eg. if molefraction of a component in a fluid is 0 - the command

fluid.getCharacterization().characterisePlusFraction()

throws and exception.

To Reproduce
fluid.getCharacterization().characterisePlusFraction()
throws and exception.

Expected behavior
PlusCharacterization should work even if a component has 0 mole fraction

Screenshots