Auto-hide the minimized chats toggle

css/converse.css

@@ -1057,6 +1057,7 @@ dl.add-converse-contact {
 #conversejs #trimmed-chatboxes {
   width: 130px;
   padding: 0;
+  display: none;
 }
 #conversejs .chatbox {
   width: 200px;

less/converse.less

@@ -1169,6 +1169,7 @@ dl.add-converse-contact {
 #conversejs #trimmed-chatboxes {
     width: 130px;
     padding: 0;
+    display: none;
 }
 
 #conversejs .chatbox {