Ajax HTTP 500 error when voting

I've had this module working on my project for a few weeks without a problem. However recently, I installed commerce and altered the node with the fivestar entity to become a product node for a commerce product. After doing this I've started to get this messge:

An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /system/ajax
StatusText: Internal Server Error
ResponseText: [{"command":"settings","settings":{"basePath":"\/","pathPrefix":"","ajaxPageState":{"theme":"customised","theme_token":"VlgtQCHA9rvi3RdbiV0Sgrnvu9Zf394dsSHoJ0OD06M"},"ajax":{"edit-vote--4":{"callback":"fivestar_ajax_submit","event":"change","url":"\/system\/ajax","submit":{"_triggering_element_name":"vote"}}}},"merge":true},{"command":"fivestarUpdate","data":"\u003Cdiv class=\u0022clearfix fivestar-average-text fivestar-average-stars fivestar-form-item fivestar-basic\u0022\u003E\u003Cdiv class=\u0022form-item form-type-fivestar form-item-vote\u0022\u003E\n \u003Cdiv class=\u0022form-item form-type-select form-item-vote\u0022\u003E\n \u003Cselect id=\u0022edit-vote--4\u0022 name=\u0022vote\u0022 class=\u0022form-select\u0022\u003E\u003Coption value=\u0022-\u0022\u003ESelect rating\u003C\/option\u003E\u003Coption value=\u002210\u0022 selected=\u0022selected\u0022\u003EGive it 1\/10\u003C\/option\u003E\u003Coption value=\u002220\u0022\u003EGive it 2\/10\u003C\/option\u003E\u003Coption value=\u002230\u0022\u003EGive it 3\/10\u003C\/option\u003E\u003Coption value=\u002240\u0022\u003EGive it 4\/10\u003C\/option\u003E\u003Coption value=\u002250\u0022\u003EGive it 5\/10\u003C\/option\u003E\u003Coption value=\u002260\u0022\u003EGive it 6\/10\u003C\/option\u003E\u003Coption value=\u002270\u0022\u003EGive it 7\/10\u003C\/option\u003E\u003Coption value=\u002280\u0022\u003EGive it 8\/10\u003C\/option\u003E\u003Coption value=\u002290\u0022\u003EGive it 9\/10\u003C\/option\u003E\u003Coption value=\u0022100\u0022\u003EGive it 10\/10\u003C\/option\u003E\u003C\/select\u003E\n\u003C\/div\u003E\n\n\u003C\/div\u003E\n\u003C\/div\u003E"}]Recoverable fatal error: Argument 1 passed to drupal_attributes() must be an array, null given, called in /home/activein/public_html/[mysite]/includes/common.inc on line 2484 and defined in drupal_attributes() (line 2376 of /home/activein/public_html/[mysite]/includes/common.inc).

Does anybody have any ideas where to start with this message? I've tried searching for this issue and found nothing.

Any help would be hugely appreciated.

Thanks