Refs #4041, default to HtmlTable if visualization ID is invalid and filled out a function doc.

core/DataTableVisualization.php

@@ -219,14 +219,14 @@ abstract class DataTableVisualization
      * Returns the visualization class by it's viewDataTable ID.
      * 
      * @param string $id The visualization ID.
-     * @return string The visualization class name.
-     * @throws \Exception if $id is not a valid visualization ID.
+     * @return string The visualization class name. If $id is not a valid ID, the HtmlTable visualization
+     *                is returned.
      */
     public static function getClassFromId($id)
     {
         $visualizationClasses = self::getAvailableVisualizations();
         if (!isset($visualizationClasses[$id])) {
-            throw new \Exception("Invalid DataTable visualization ID: '$id'.");
+            return $visualizationClasses['table'];
         }
         return $visualizationClasses[$id];
     }

core/ViewDataTable.php

@@ -408,7 +408,8 @@ class ViewDataTable
     }
 
     /**
-     * TODO
+     * Sets visualization properties using data in a visualization's default property values
+     * array.
      */
     private function setVisualizationPropertiesFromMetadata($properties)
     {