Webservices calculates mol wt for in-line HELM with unused connection points

[ClairePA]

Structures with unused connection points should not have a calculated mol wt.

Example HELM strings where there are unused connection points that can be used for testing.

PEPTIDE1{[C(=O)[C@H](C)N([*:1])C]}$$$$
PEPTIDE1{[C(=O)[C@H](C)N(*)C |$_;;;;;;;_R1;;;$]}$$$$
PEPTIDE1{[[*:2]C(=O)[C@H](C)N([*:1])C]}$$$$