deal with polygons of 0 area

package.json

@@ -1,6 +1,6 @@
 {
   "name": "roughjs",
-  "version": "4.0.0",
+  "version": "4.0.1",
   "description": "Create graphics using HTML Canvas or SVG with a hand-drawn, sketchy, appearance.",
   "main": "bundled/rough.cjs.js",
   "module": "bin/rough.js",

src/fillers/scan-line-hachure.ts

@@ -74,6 +74,9 @@ function straightHachureLines(points: Point[], o: ResolvedOptions): Line[] {
       }
       return (e1.ymax - e2.ymax) / Math.abs((e1.ymax - e2.ymax));
     });
+    if (!edges.length) {
+      return lines;
+    }
 
     // Start scanning
     let activeEdges: ActiveEdgeEntry[] = [];