Fix ultra-rare case of jiggle = 0

src/jiggle.js

@@ -1,6 +1,10 @@
 /**
- * @return {number} a random number.
+ * @return {number} a very small non-zero random number.
  */
 export default function() {
-  return (Math.random() - 0.5) * 1e-6;
+  let rand;
+  do {
+    rand = (Math.random() - 0.5) * 1e-6;
+  while (rand === 0);
+  return rand;
 }