PLT-6885/PLT-6888 Fix custom emojis (#6694)

* Fix custom emojis

* Fix custom emoji reactions

webapp/components/post_view/reaction/index.js

@@ -20,7 +20,7 @@ function makeMapStateToProps() {
         if (Emoji.EmojiIndicesByAlias.has(ownProps.emojiName)) {
             emoji = Emoji.Emojis[Emoji.EmojiIndicesByAlias.get(ownProps.emojiName)];
         } else {
-            emoji = ownProps.emojis[ownProps.emojiName];
+            emoji = ownProps.emojis.get(ownProps.emojiName);
         }
 
         return {