[Bug] LCT: Strange things with S

[smtdm]

Describe the bug S has been fixed (it now can have 6 bonds). But this breaks some rendering. Maybe we need to redefine how valence electrons are used in the mod.

To Reproduce

1. Take LCT with S
2. Add some stuff
3. ???
4. Profit (or crash)

Expected behavior S (and Se and Te) should be able to make 6 bonds, like in H2SO4. When adding 4 H's next to S, the final 2 lone electrons need to be rendered somewhere (first screenshot)

Screenshots

An attempt to fix S:

Additional context

[pixar02]

Is caused because you "replace" the item in the grid with the item in your cursor. So we need to make sure we can't "replace"/ "swap" items (grid <-> cursor)