title: Array error on WooCommerce checkout page
body: <p>I am getting an error when I try to checkout with PayPal in WooCommerce. I have no idea what's causing it.</p>
  
  <p>I also have a SagePay plugin, but it happens on either option, no matter what.</p>
  
  <pre><code>Warning: array_merge() [function.array-merge]: Argument #1 is not an array in /home/beggar/public_html/development/wp-includes/post.php on line 2996
  {"result":"success","redirect":"https:\/\/www.sandbox.paypal.com\/webscr?test_ipn=1&amp;cmd=_cart&amp;business=michael%40thelondonbranch.com&amp;no_note=1¤cy_code=GBP&amp;charset=UTF-8&amp;rm=1&amp;upload=1&amp;return=http%3A%2F%2Fexample.com%2Fdevelopment%2Fthank-you%2F%3Futm_nooverride%3D1&amp;cancel_return=http%3A%2F%2Fexample.com%2Fdevelopment%2F%3Fcancel_order%3Dtrue%26_n%3Dc479c487a6&amp;page_style=&amp;invoice=WC-¬ify_url=http%3A%2F%2Fexample.com%2Fdevelopment%2F%3FpaypalListener%3Dpaypal_standard_IPN&amp;no_shipping=1&amp;discount_amount_cart=0.00&amp;item_name_1=Order+%23+-+&amp;quantity_1=1&amp;amount_1=0.00"}
  </code></pre>
  
  <p>This isn't just a warning it seems, as no order is placed in the admin, or emails sent.</p>
  
  <p>I am absolutely stumped on this and it's pretty critical.</p>
  
  <p>Any help greatly appreciated as this is my first time using WooCommerce.</p>