_removeVertexFromFace( vertex, face ) {

		if ( vertex === face.outside ) {

			// fix face.outside link

			if ( vertex.next !== null && vertex.next.face === face ) {

				// face has at least 2 outside vertices, move the 'outside' reference

				face.outside = vertex.next;

			} else {

				// vertex was the only outside vertex that face had

				face.outside = null;

			}

		}

		this.assigned.remove( vertex );

		return this;

	}
Removes a vertex from the 'assigned' list of vertices and from the given face.
It also makes sure that the link from 'face' to the first vertex it sees in 'assigned'
is linked correctly after the removal.

@private
@param {VertexNode} vertex - The vertex to remove.
@param {Face} face - The target face.
@return {ConvexHull} A reference to this convex hull.