getDatatypes: throw more meaningful exception if no data is present

extensions/DatatypeTrait.php

@@ -74,12 +74,17 @@ trait DatatypeTrait {
      *
      * @access public
      *
+     * @uses getDatatypeFromString
+     *
      * @return array|bool
      */
     public function getDatatypes() {
         if (empty($this->data)) {
             $this->data = $this->parse_string();
         }
+        if (!is_array($this->data)) {
+            throw new \Exception('No data set yet.');
+        }
 
         $result = [];
         foreach ($this->titles as $cName) {