fix: not checking for guild when creating a channel

src/stores/ChannelStore.js

@@ -55,7 +55,7 @@ class ChannelStore extends DataStore {
   add(data, guild, cache = true) {
     const existing = this.get(data.id);
     if (existing && existing._patch && cache) existing._patch(data);
-    if (existing) {
+    if (existing && guild) {
       guild.channels.add(existing);
       return existing;
     }