found two more getter conversion cases

src/mode/cam/ops.js

@@ -1029,7 +1029,6 @@
                             move(0, -y4);
                         });
                         poly.points.pop();
-                        poly.length--;
                         slice.camTrace = { tool: tool.getID(), rate: op.feed, plunge: op.rate };
                         slice.camLines = [ poly ];
                         slice.output()

src/mode/cam/slice.js

@@ -337,7 +337,6 @@
             for (let poly of noff) {
                 if (poly.open && poly.first().isMergable2D(poly.last())) {
                     poly.points.pop();
-                    poly.length--;
                     poly.open = false;
                 }
             }