Fix some javascript errors in rare situations (#1490441)

CHANGELOG

@@ -21,6 +21,7 @@ CHANGELOG Roundcube Webmail
 - Fix so imap folder attribute comparisons are case-insensitive (#1490466)
 - Fix bug where new messages weren't added to the list in search mode
 - Fix wrong positioning of message list header on page scroll in Webkit browsers (#1490035)
+- Fix some javascript errors in rare situations (#1490441)
 
 RELEASE 1.1.2
 -------------

program/js/app.js

@@ -8040,7 +8040,7 @@ function rcube_webmail()
   // get the IMP mailbox of the message with the given UID
   this.get_message_mailbox = function(uid)
   {
-    var msg = this.env.messages ? this.env.messages[uid] : {};
+    var msg = (this.env.messages && uid ? this.env.messages[uid] : null) || {};
     return msg.mbox || this.env.mailbox;
   };
 

program/js/list.js

@@ -565,6 +565,10 @@ drag_row: function(e, id)
  */
 click_row: function(e, id)
 {
+  // sanity check
+  if (!id || !this.rows[id])
+    return false;
+
   // don't do anything (another action processed before)
   if (!this.is_event_target(e))
     return true;