bug add fluids

[EvenSol]

Describe the bug
a little bug I found
gas_plus_aq = addfluids(pre_aq_fluid, pre_gas_fluid);

TPflash(gas_plus_aq);

gives different result than
gas_plus_aq = addfluids(pre_gas_fluid, pre_aq_fluid);

TPflash(gas_plus_aq);

(the order of the arguments is important)

addfluids is only doing: p = neqsim.thermo.system.SystemInterface.addFluids(fluid1,fluid2);

To Reproduce

[asmfstatoil]

I tried this out, but could not reproduce, you can try to reproduce using code from #1368

[dupuypablo]

I have still issues with this. I have a matlab implementation and is therefore not straightforward for me to reproduce.

Note: I have Pseudocomponent in my case. In general I have two very different phases, one gas and one HC liquid. It might be that if the one I try to add has a PseudoComponent that is not included in the first one, then it crashes. But there might be other non-symmetries.