use project-specific custom field api.

app/assets/javascripts/timelines/TimelineLoader.js

@@ -676,6 +676,10 @@ Timeline.TimelineLoader = (function () {
     };
 
     TimelineLoader.prototype.registerGlobalElements = function () {
+      var projectPrefix = this.globalPrefix + 
+                          this.options.project_prefix +
+                          "/" +
+                          this.options.project_id;
 
       this.loader.register(
           Timeline.Status.identifier,
@@ -688,7 +692,7 @@ Timeline.TimelineLoader = (function () {
           { url : this.globalPrefix + '/colors.json' });
       this.loader.register(
           Timeline.CustomFields.identifier,
-          { url : this.globalPrefix + '/custom_fields.json' });
+          { url : projectPrefix + '/planning_element_custom_fields.json' });
       this.loader.register(
           Timeline.ProjectType.identifier,
           { url : this.globalPrefix + '/project_types.json' });

app/assets/javascripts/timelines/ui.js

@@ -867,7 +867,10 @@ jQuery.extend(Timeline, {
     var header = function(key) {
       var th = jQuery('<th></th>');
       if (key.substr(0, 3) === "cf_") {
-        th.append(timeline.custom_fields[parseInt(key.substr(3), 10)].name);
+        var timeline_id = parseInt(key.substr(3), 10);
+        if (timeline.custom_fields[timeline_id]) {
+          th.append(timeline.custom_fields[timeline_id].name);
+        }
       } else {
         th.append(timeline.i18n('timelines.filter.column.' + key));
       }