FIX Fatal error: Call to a member function toOptionArray() on a non-object

Fix Fatal error: Call to a member function toOptionArray() on a non-object



replace

$optionArray = $sourceModel->toOptionArray($fieldType == ‘multiselect’);

with

 if ( is_object($sourceModel) ) {
                $field->setValues($sourceModel->toOptionArray($fieldType == 'multiselect') );
}