fix corner case with identical offset fill points

js/geo-point.js

@@ -194,6 +194,10 @@ var gs_base_point = exports;
         var c1 = dot(w, v);
         var c2 = dot(v, v);
         var b = c1 / c2;
+        if (isNaN(b)) {
+            // console.log('nan', {p, l1, l2, v, w, c1, c2});
+            b = 0;
+        }
         var pb = {x: l1.x + b * v.x, y: l1.y + b * v.y};
         return d(p, pb);
     }

js/kiri-print.js

@@ -769,6 +769,13 @@ let gs_kiri_print = exports;
 
                 // go back to start and try again
                 if (!found) {
+                    if (start === 0 && lastIndex === -1) {
+                        console.log('infinite loop', lines, {
+                            marked, options, i, group, start, lastIndex,
+                            points: lines.map(p => p.index).join(', ')
+                        });
+                        break;
+                    }
                     start = 0;
                     lastIndex = -1;
                     continue;