Edit Google.php

Closes #3466734

modules/charts_google/src/Plugin/chart/Library/Google.php

@@ -564,6 +564,9 @@ class Google extends ChartBase implements ContainerFactoryPluginInterface {
       ];
     }
     else {
+      if (!isset($data[0])) {
+        $data[0] = [];
+      }
       array_unshift($data[0], '');
     }
     // Ensure consistent column count.