Fix alpine morpher

Skip morphing if htmlElement is an empty string.

Author: imankulov

django_unicorn/static/unicorn/js/morphers/alpine.js

@@ -11,7 +11,9 @@ See https://www.django-unicorn.com/docs/custom-morphers/#alpine for more informa
  }
 
  morph(dom, htmlElement) {
- return window.Alpine.morph(dom, htmlElement, this.getOptions());
+ if (htmlElement) {
+ return window.Alpine.morph(dom, htmlElement, this.getOptions());
+ }
  }
 
  getOptions() {