Fix cold colours in activity column of topic lists

app/assets/javascripts/discourse/models/topic.js

@@ -112,24 +112,22 @@ Discourse.Topic = Discourse.Model.extend({
 
   // The coldmap class for the age of the topic
   ageCold: function() {
-    var createdAt, createdAtDays, daysSinceEpoch, lastPost, nowDays;
-    if (!(lastPost = this.get('last_posted_at'))) return;
+    var createdAt, daysSinceEpoch, lastPost, lastPostDays, nowDays;
     if (!(createdAt = this.get('created_at'))) return;
+    if (!(lastPost = this.get('last_posted_at'))) lastPost = createdAt;
     daysSinceEpoch = function(dt) {
       // 1000 * 60 * 60 * 24 = days since epoch
       return dt.getTime() / 86400000;
     };
 
     // Show heat on age
     nowDays = daysSinceEpoch(new Date());
-    createdAtDays = daysSinceEpoch(new Date(createdAt));
-    if (daysSinceEpoch(new Date(lastPost)) > nowDays - 90) {
-      if (createdAtDays < nowDays - 60) return 'coldmap-high';
-      if (createdAtDays < nowDays - 30) return 'coldmap-med';
-      if (createdAtDays < nowDays - 14) return 'coldmap-low';
-    }
+    lastPostDays = daysSinceEpoch(new Date(lastPost));
+    if (nowDays - lastPostDays > 60) return 'coldmap-high';
+    if (nowDays - lastPostDays > 30) return 'coldmap-med';
+    if (nowDays - lastPostDays > 14) return 'coldmap-low';
     return null;
-  }.property('age', 'created_at'),
+  }.property('age', 'created_at', 'last_posted_at'),
 
   viewsHeat: function() {
     var v = this.get('views');