Don't overwrite default avatar with `undefined`

src/converse-chatview.js

@@ -249,6 +249,7 @@
                 render () {
                     this.el.innerHTML = tpl_chatbox_head(
                         _.extend(this.model.toJSON(), {
+                            '_converse': _converse,
                             'avatar_width': _converse.chatview_avatar_width,
                             'avatar_height': _converse.chatview_avatar_height,
                             'info_close': __('Close this chat box'),

src/converse-core.js

@@ -878,9 +878,10 @@
             },
 
             initialize (attributes) {
-                const { jid } = attributes;
-                const bare_jid = Strophe.getBareJidFromJid(jid).toLowerCase();
-                const resource = Strophe.getResourceFromJid(jid);
+                const { jid } = attributes,
+                      bare_jid = Strophe.getBareJidFromJid(jid).toLowerCase(),
+                      resource = Strophe.getResourceFromJid(jid);
+
                 attributes.jid = bare_jid;
                 this.set(_.assignIn({
                     'fullname': bare_jid,

src/templates/chatbox_head.html

@@ -4,7 +4,7 @@
         <img alt="User Avatar"
             class="avatar"
             height="{{{o.avatar_height}}}px" width="{{{o.avatar_width}}}px"
-            src="data:{{{o.image_type}}};base64,{{{o.image}}}"/>
+            src="data:{{{o.image_type || o._converse.DEFAULT_IMAGE_TYPE}}};base64,{{{o.image || o._converse.DEFAULT_IMAGE}}}"/>
     {[ } ]}
     <div class="chat-title">
         {[ if (o.url) { ]}