Ignore incoming empty chat messages.

Fixes #62.

lib/pleroma/web/chat_channel.ex

@@ -14,11 +14,14 @@ def handle_info(:after_join, socket) do
   end
 
   def handle_in("new_msg", %{"text" => text}, %{assigns: %{user_name: user_name}} = socket) do
+    text = String.trim(text)
+    if String.length(text) > 0 do
       author = User.get_cached_by_nickname(user_name)
       author = Pleroma.Web.MastodonAPI.AccountView.render("account.json", user: author)
       message = ChatChannelState.add_message(%{text: text, author: author})
 
       broadcast! socket, "new_msg", message
+    end
     {:noreply, socket}
   end
 end