Fix: don't pass nextStep.element to onbeforechange callback if it s not exists yet

Author: gooddaytoday

src/core/steps.js

@@ -59,7 +59,8 @@ export function nextStep() {
   if (typeof this._introBeforeChangeCallback !== "undefined") {
     continueStep = this._introBeforeChangeCallback.call(
       this,
-      nextStep && nextStep.element
+      nextStep &&
+        (elementBySelectorNotExists(nextStep) ? undefined : nextStep.element)
     );
   }
 
@@ -79,16 +80,23 @@ export function nextStep() {
     return;
   }
 
-  if (
-    typeof nextStep._element === "string" &&
-    document.querySelector(nextStep._element) === null
-  ) {
+  if (elementBySelectorNotExists(nextStep)) {
     waitForElement(nextStep._element, () => showElement.call(this, nextStep));
   } else {
     showElement.call(this, nextStep);
   }
 }
 
+/**
+ * Return true if element locates by selector and doesn't exists yet
+ */
+function elementBySelectorNotExists(step) {
+  return (
+    typeof step._element === "string" &&
+    document.querySelector(step._element) === null
+  );
+}
+
 /**
  * Go to previous step on intro
  *