TagField lazy load shouldnt render Options

TagField should only render options if the lazy load value isn't set. Options from here come from subsequent POSTs, and rendering the options for every request significantly slows down both the form generation and render.

src/TagField.php

@@ -262,6 +262,20 @@ class TagField extends DropdownField
         $ids = $values->column($this->getTitleField());
 
         $titleField = $this->getTitleField();
+        
+        if ($this->shouldLazyLoad) {
+            // only render options that are selected as everything else should be lazy loaded, and or loaded by the form
+            foreach ($values as $value) {
+                $options->push(
+                    ArrayData::create(array(
+                        'Title' => $value->$titleField,
+                        'Value' => $value->Title,
+                        'Selected' => true, // only values are iterated.
+                    ))
+                );
+            }
+            return $options;
+        }
 
         foreach ($source as $object) {
             $options->push(