Fix rendering of MUC sidebar.

Looks like styling broke after a rebase.

src/plugins/muc-views/styles/muc-occupants.scss

@@ -22,13 +22,24 @@
         }
 
         .box-flyout {
-            .occupants {
+
+            converse-muc-sidebar {
                 display: flex;
-                flex-direction: column;
+                height: 100%;
+                flex-direction: row;
                 justify-content: space-between;
                 overflow: visible;
                 background-color: var(--occupants-background-color);
                 border-left: var(--occupants-border-left);
+            }
+
+            .occupants {
+                display: flex;
+                height: 100%;
+                flex-direction: column;
+                justify-content: space-between;
+                overflow-y: visible;
+                overflow-x: auto;
 
                 .occupants-header--title {
                     display: flex;

src/plugins/muc-views/templates/muc-chatarea.js

@@ -44,7 +44,7 @@ export default (el) => {
         </div>
         ${el.model ? html`
             <converse-muc-sidebar
-                class="occupants ${el.shouldShowSidebar() ? sidebar_classes : 'col-xs-0 hidden' }"
+                class="${el.shouldShowSidebar() ? sidebar_classes : 'col-xs-0 hidden' }"
                 jid=${el.jid}
                 @mousedown=${(ev) => el.onMousedown(ev)}></converse-muc-sidebar>` : '' }`
 };