fix UI for group curated list editing

When creating or editing a list, the group selection dropdown will only appear if the user selects "group" as the curation option (or it is already selected).

- fix typo in bookwyrm.js comments
- add data-hides trigger for hiding elements after they have been unhidden, where simple toggles are not the right approach

bookwyrm/static/js/bookwyrm.js

@@ -28,6 +28,12 @@ let BookWyrm = new class {
                 this.revealForm.bind(this))
             );
 
+        document.querySelectorAll('[data-hides]')
+            .forEach(button => button.addEventListener(
+                'change',
+                this.hideForm.bind(this))
+            );
+
         document.querySelectorAll('[data-back]')
             .forEach(button => button.addEventListener(
                 'click',
@@ -119,7 +125,7 @@ let BookWyrm = new class {
     }
 
     /**
-     * Toggle form.
+     * Show form.
      *
      * @param  {Event} event
      * @return {undefined}
@@ -127,10 +133,26 @@ let BookWyrm = new class {
     revealForm(event) {
         let trigger = event.currentTarget;
         let hidden = trigger.closest('.hidden-form').querySelectorAll('.is-hidden')[0];
-
-        this.addRemoveClass(hidden, 'is-hidden', !hidden);
+        // if the form has already been revealed, there is no '.is-hidden' element
+        // so this doesn't really work as a toggle
+        if (hidden) {
+          this.addRemoveClass(hidden, 'is-hidden', !hidden);
+        }
     }
 
+    /**
+     * Hide form.
+     *
+     * @param  {Event} event
+     * @return {undefined}
+     */
+    hideForm(event) {
+        let trigger = event.currentTarget;
+        let targetId = trigger.dataset.hides
+        let visible = document.getElementById(targetId)
+        this.addRemoveClass(visible, 'is-hidden', true);
+  }
+
     /**
      * Execute actions on targets based on triggers.
      *
@@ -227,7 +249,7 @@ let BookWyrm = new class {
     }
 
     /**
-     * Check or uncheck a checbox.
+     * Check or uncheck a checkbox.
      *
      * @param  {string}  checkbox - id of the checkbox
      * @param  {boolean} pressed  - Is the trigger pressed?