GUI fails to show the last layer before silk

[KaiMartin]

There is a condition during which the PCB GUI does not show the contents of the last but one layer, although this layer is active. To reproduce:

1) open pcb (GTK-GUI)
2) draw a rectangle on the last layer above the silk layer
3) systematically deactivate all layers. Start from the top and go to bottom.
4) activate the layer above silk
PCB does not show the rectangle. New objects in this layer are omitted, too.

---<)kaimartin(>---

[Andrew Poelstra (asp11)]

This was fixed by the new layer selector (commit 2948179).