Fix height of modal during account creation steps (#418)

* Don't reopen an already open modal

* Avoid changing height of modal during wizard steps

app/javascript/controllers/modal_controller.js

@@ -3,7 +3,8 @@ import { Controller } from "@hotwired/stimulus"
 // Connects to data-controller="modal"
 export default class extends Controller {
   connect() {
-    this.element.showModal();
+    if (this.element.open) return
+    else this.element.showModal()
   }
 
   // Hide the dialog when the user clicks outside of it