foodcrud渲染不渲染表格

Question

When I execute this GroceryCrud PHP code:

$crud = new grocery_CRUD();

$crud->set_theme('flexigrid');
$crud->set_table('store');
$crud->set_subject('Store');

$output = $crud->render();

echo "<pre>Here is the table:";
print_r($output);
echo "</pre>";
die();

I get the following output even though the 'store' table exists in the database and there is one record in the table:

Here is the table:stdClass Object
(
    [js_files] => Array
        (
            [32fd432b4478200b5aacd62b65d5bdc269337910] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery-1.11.1.min.js
            [c7339f3bd6b575a9439e9d03677a69f742a52379] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/jquery.noty.js
            [664ddadc07d0d7e4933e1295d352922418e257a8] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/config/jquery.noty.config.js
            [1e5c41adc3783d74df037a01f5c2175a824705a1] => http://www.everythingnow.uk/assets/grocery_crud/js/common/lazyload-min.js
            [d04ba7f0d55dda1d4ba9b6532414c653c58b0318] => http://www.everythingnow.uk/assets/grocery_crud/js/common/list.js
            [2d2b031fb606852768dc4c9a3c457545558cc924] => http://www.everythingnow.uk/assets/grocery_crud/themes/flexigrid/js/cookies.js
            [6629a324ade6d489aff77292cb02e31d9188a6bb] => http://www.everythingnow.uk/assets/grocery_crud/themes/flexigrid/js/flexigrid.js
            [5238a822ff2c6cced38a61590ac6debcc847bc0b] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/jquery.form.min.js
            [41101518af3f8fb416f60152aa019d963ae9293b] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/jquery.numeric.min.js
            [8823261dedf8eda49cfa2a7a528b5182350a90ae] => http://www.everythingnow.uk/assets/grocery_crud/themes/flexigrid/js/jquery.printElement.min.js
            [6279df8612f557f3151c02ed3dfc5d97f491e9cf] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/jquery.fancybox-1.3.4.js
            [d24105860047fc8ef3893d8892bb13d5cb2e8455] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/jquery.easing-1.3.pack.js
            [2ea588263ae884c476a96f40dc6cedd5316bbd57] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/ui/jquery-ui-1.10.3.custom.min.js
        )

    [js_lib_files] => Array
        (
            [32fd432b4478200b5aacd62b65d5bdc269337910] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery-1.11.1.min.js
            [c7339f3bd6b575a9439e9d03677a69f742a52379] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/jquery.noty.js
            [664ddadc07d0d7e4933e1295d352922418e257a8] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/config/jquery.noty.config.js
            [1e5c41adc3783d74df037a01f5c2175a824705a1] => http://www.everythingnow.uk/assets/grocery_crud/js/common/lazyload-min.js
            [d04ba7f0d55dda1d4ba9b6532414c653c58b0318] => http://www.everythingnow.uk/assets/grocery_crud/js/common/list.js
            [2ea588263ae884c476a96f40dc6cedd5316bbd57] => http://www.everythingnow.uk/assets/grocery_crud/js/jquery_plugins/ui/jquery-ui-1.10.3.custom.min.js
        )

    [js_config_files] => Array
        (
        )

    [css_files] => Array
        (
            [f1731e27afe02ab899b16daf8ae4a5ac8ac05d4e] => http://www.everythingnow.uk/assets/grocery_crud/themes/flexigrid/css/flexigrid.css
            [ed7c731212886ffa5071a6db738fbff8be24bfa6] => http://www.everythingnow.uk/assets/grocery_crud/css/jquery_plugins/fancybox/jquery.fancybox.css
            [3e3f44ffabdcdd9017fa9db5262ce0465dde1322] => http://www.everythingnow.uk/assets/grocery_crud/css/ui/simple/jquery-ui-1.10.1.custom.min.css
        )

    [output] => 

I have tested that crud is loading ok and that it is connecting to the 'store' table in the database.

Anyone have an idea as to why grocerycrud is not rendering the table?