[polari] chatView: Don't access unset property

[Florian Müllner <fmuellner src gnome org>]

commit cde6b66ed2a49e29c0e540b0d6b856ebb543d585
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Feb 16 20:08:43 2017 +0100

    chatView: Don't access unset property
    
    We attach a timestamp of the last activity to nick tags to decide
    whether to show corresponding status messages or not. However
    this monkey-patched property is unset if there hasn't been any
    activity from the nick - make sure to handle that case properly
    instead of using an undefined value in a computation.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=778793

 src/chatView.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/chatView.js b/src/chatView.js
index 8f9de8e..2ca8d9a 100644
--- a/src/chatView.js
+++ b/src/chatView.js
@@ -1031,7 +1031,7 @@ const ChatView = new Lang.Class({
     _shouldShowStatus: function(nick) {
         let nickTag = this._lookupTag('nick' + nick);
 
-        if (!nickTag)
+        if (!nickTag || !nickTag._lastActivity)
             return false;
 
         let time = GLib.get_monotonic_time();