Fixed property access

src/Models/Traits/HasTitle.php

@@ -15,6 +15,11 @@ trait HasTitle
         return $this;
     }
 
+    public function getTitle()
+    {
+        return $this->title;
+    }
+
     protected function initTitle()
     {
         $this->title = $this->defaultTitle();

src/Models/TreeMapChartModel.php

@@ -33,7 +33,7 @@ class TreeMapChartModel extends BaseChartModel
 
     public function addBlock($title, $value, $extras = [])
     {
-        return $this->addSeriesBlock($this->title, $title, $value, $extras);
+        return $this->addSeriesBlock($this->getTitle(), $title, $value, $extras);
     }
 
     public function addSeriesBlock($seriesName, $title, $value, $extras = [])