When building signalbox, signals stay hidden

[Ves]

When building a signalbox with ad932b7a9407a01c69bae58851fc76c9c767aaf7 the buildable signals do not pop up in the build menu.
Neither does clicking on existing signalboxes show the buildable signals.

[jamespetts]

I think that I have fixed this; would you be able to re-test? I should be grateful.

[Ves]

Appears to be fixed! thanks!