Fix runtime react errors for various parts of the app

These are just the ones that were causing console flooding on reload in development.

* Elements in a list need a `key`
* `super()` needs to be supplied with the same props as the parent
* `<div>` (AccessibleButton) cannot be a descendant of `<p>` - this was a problem in the NewRoomIntro "Add topic" button
* `label` is a non-boolean property and cannot receive "false"

src/components/views/rooms/NewRoomIntro.tsx

@@ -106,7 +106,11 @@ const NewRoomIntro = () => {
             topicText = _t("Topic: %(topic)s ", { topic });
         } else if (canAddTopic) {
             topicText = _t("<a>Add a topic</a> to help people know what it is about.", {}, {
-                a: sub => <AccessibleButton kind="link" onClick={onTopicClick}>{ sub }</AccessibleButton>,
+                a: sub => <AccessibleButton
+                    kind="link"
+                    element="span"
+                    onClick={onTopicClick}
+                >{ sub }</AccessibleButton>,
             });
         }