Made nickname form "unrender" before rerendering, made nickname error show again

src/converse-muc-views.js

@@ -1680,12 +1680,11 @@ converse.plugins.add('converse-muc-views', {
             },
 
             showNicknameForm () {
-                const isNicknameFormRendered = !!this.el.querySelector('.muc-nickname-form');
-                if (isNicknameFormRendered) {
-                    this.showNicknameFormContents();
-                } else {
-                    this.renderNicknameForm();
+                const nicknameForm = this.el.querySelector('.muc-nickname-form');
+                if (nicknameForm) {
+                    u.removeElement(nicknameForm);
                 }
+                this.renderNicknameForm();
             },
 
             /**
@@ -1722,11 +1721,12 @@ converse.plugins.add('converse-muc-views', {
                     __('Choose a nickname to enter') :
                     __('Please choose your nickname');
 
-                const html = tpl_chatroom_nickname_form(Object.assign({
+                const templateData = Object.assign({
                     heading,
                     'label_nickname': __('Nickname'),
                     'label_join': __('Enter groupchat'),
-                }, this.model.toJSON()));
+                }, this.model.toJSON());
+                const html = tpl_chatroom_nickname_form(templateData);
 
                 if (_converse.muc_show_logs_before_join) {
                     const container = this.el.querySelector('.muc-bottom-panel');

src/templates/chatroom_nickname_form.html

@@ -2,6 +2,7 @@
     <form class="converse-form chatroom-form converse-centered-form">
         <fieldset class="form-group">
             <label>{{{o.heading}}}</label>
+            <p class="validation-message">{{{o.nickname_validation_message}}}</p>
             <input type="text" required="required" name="nick" value="{{{o.nickname}}}"
                    class="form-control {{o.error_class}}" placeholder="{{{o.label_nickname}}}"/>
         </fieldset>