[2.1.9] Roboport connection lines disappear when both of the roboports are out of view

[FilipForFico]

This is just a visual bug and not really that important.

Steps to reproduce: place two roboports far apart so their logistic areas connect. It is important that they are active (have power). Now get a roboport in hand and a line connecting the first two should appear. Now zoom all the way in to make both the roboports go out of view. The line connecting them disappears.

The expected behaviour is for the line to still be drawn.

Let me know if I should attach a screenshot or something.

[Rseding91]

Thanks for the report. This is now fixed for the next release.