Fix live updates to reaction row buttons

This makes the reaction row buttons take the current count as prop as an easy
way of ensuring they always trigger an update when the count changes.

Fixes https://github.com/vector-im/riot-web/issues/9954

src/components/views/messages/ReactionsRow.js

@@ -116,6 +116,7 @@ export default class ReactionsRow extends React.PureComponent {
             return <ReactionsRowButton
                 key={content}
                 content={content}
+                count={count}
                 mxEvent={mxEvent}
                 reactionEvents={events}
                 myReactionEvent={myReactionEvent}

src/components/views/messages/ReactionsRowButton.js

@@ -27,6 +27,8 @@ export default class ReactionsRowButton extends React.PureComponent {
         mxEvent: PropTypes.object.isRequired,
         // The reaction content / key / emoji
         content: PropTypes.string.isRequired,
+        // The count of votes for this key
+        count: PropTypes.number.isRequired,
         // A Set of Martix reaction events for this key
         reactionEvents: PropTypes.object.isRequired,
         // A possible Matrix event if the current user has voted for this type
@@ -77,12 +79,7 @@ export default class ReactionsRowButton extends React.PureComponent {
     render() {
         const ReactionsRowButtonTooltip =
             sdk.getComponent('messages.ReactionsRowButtonTooltip');
-        const { content, reactionEvents, myReactionEvent } = this.props;
-
-        const count = reactionEvents.size;
-        if (!count) {
-            return null;
-        }
+        const { content, count, reactionEvents, myReactionEvent } = this.props;
 
         const classes = classNames({
             mx_ReactionsRowButton: true,