Fixes removeMiddlePoints in LinkModel.ts.

[ELennard]

RemoveMiddlePoints removed the first point from points, while it should not delete the startpoint.

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What?

Fixes the removeMiddlePoints function in the LinkModel.

Why?

The removeMiddlePoints function removes the startpoint of a link. The function should only remove points between start and endpoint.

How?

Updated the function to skip the first point.

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