Vle fix

[yalinli2]

Main things:

1. Checks if the chemical has Tc/Pc first, prior to comparison.
2. The P loop re-iterates the same index list the T-branch already consumed, without excluding indices it removed. A chemical above both Tc and Pc gets nonzero.remove(i) called twice, raising KeyError on the second call.
3. There was a typo, the first HNK_index should LNK_index.
4. chemicals._heavy_solutes is a fixed-size array computed once for the compile-time heavy chemicals, but HNK_index can grow at runtime with newly-excluded supercritical chemicals, so multiplying heavy_mol (sized to the grown HNK_index) by the unextended _heavy_solutes array raises a shape-mismatch ValueError.

Reproduction

import thermosteam as tmo

chemicals = tmo.Chemicals(['H2O', 'CH4'])
tmo.settings.set_thermo(chemicals)
s = tmo.Stream('s', H2O=10, CH4=5, units='kg/hr', phase='g')
s.vle(T=675.15, P=1.05e7)  # CH4 is above both Tc (~190.6 K) and Pc (~4.6 MPa)
# KeyError: 1

[yoelcortes]

Looks good, thank you!