fix poly cleanup return

notes.md

@@ -16,7 +16,6 @@ NEXT
 
 # FDM
 
-* `B` miter acute angles (benchy + square render)
 * `B` fix preview/gcode layer size (first layer)
 * `B` fix adaptive slicing with multi-extruder
 * `B` fix supports with grouped parts

src/geo/polygon.js

@@ -1159,12 +1159,14 @@
             clip = clib.Clipper,
             clean = clip.CleanPolygon(this.toClipper()[0], CONF.clipperClean),
             poly = fromClipperPath(clean, this.getZ());
+        if (poly.length === 0) return this;
         if (deep && this.inner) {
             poly.inner = this.inner.map(inr => inr.clean(false, poly));
         }
         poly.parent = parent || this.parent;
         poly.area2 = this.area2;
-        return poly || this;
+        poly.open = this.open;
+        return poly;
     };
 
     PRO.toClipper = function(inout,debug) {

src/kiri/render.js

@@ -164,7 +164,7 @@
 
             polys.forEach(poly => {
                 const contour = [];
-                poly = poly.miter();
+                poly = poly.clean().miter();
                 // if (poly.debug) {
                 //     const save = this.current;
                 //     this.setLayer('debug.acute', 0xff0000).addPoly(poly, {thin:true});