fix(editor): a track bent by its second control vector is drawn bent: the straightening of a straight with control vectors (world/Track.cpp) checked the first vector twice, so with it left along the straight the second one, dragged with the gizmo, changed the data but not the track drawn; now a straight only where both vectors lie along it or aren't given. A track bent by hand into an S between two points dragged is labelled with its length (L 77 m), not with a radius of many kilometres read off it; the "K: split here" by the cursor isn't shown while a point is dragged; Ctrl+Z takes away the warning by the cursor of what it took back (the paths that left the kept design). The tutorial clips of editing recorded again: selecting and fixing without the gizmo (a joint dragged, the warning read, Ctrl+Z), and the new one of editing with the gizmo (Q, a control vector dragged bending the track, W, E)

application/editormode.cpp

@@ -965,6 +965,8 @@ void editor_mode::restore_terrain(EditorSnapshot &Snapshot)
 void editor_mode::undo_last()
 {
     first_step_done(first_step::undo);
+    // the warning by the cursor told of the step taken back now: "Ctrl+Z takes it back" is done
+    ui()->drop_refusal();
     // a change of the terrain made a moment ago is a step of its own before it's taken back
     m_history_busy = true;
     terrain_history_step();