Fix tooltip location in plots

[anotheruserofgithub]

Related Issues

model Test
  final input Real params[:] = {time * i for i in 1:3};
equation
  annotation(experiment(StartTime = 1, StopTime = 2));
end Test;

Simulate this model, then plot params as an array plot and try to display the tooltip around the last point (3, 3).

Purpose

The above test will fail!
It also shows how the fix makes "picking the points" much smoother and funnier.

Approach

Fixed a buggy condition (typo) in a function that checks whether a point belongs the a line segment with margins.

[anotheruserofgithub]

@adeas31 Would you mind having a look? I saw this when working on diagram visualization, but forgot to push it.