Warning: addcslashes() expects parameter 1 to be string, array given

I have a custom module that I'm using to change a text views exposed filter into checkboxes. I thought that it was working and the Warning was harmless, but apparently it isn't actually functioning correctly.

Warning: addcslashes() expects parameter 1 to be string, array given in DatabaseConnection->escapeLike() (line 965 of /Applications/MAMP/htdocs/includes/database/database.inc).

The code for the module is:

<?php

function dropdown_bartab_form_views_exposed_form_alter(&$form, &$form_state) {
  $field_id = 'field_venue_bar_tab';

  // Only alter forms with the necessary field
  if (isset($form[$field_id .'_value'])) {

// Build a query to get all node ids having the specified field
$query = new EntityFieldQuery();
$results = $query->entityCondition('entity_type', 'node')
                  ->fieldCondition($field_id, 'value', 'NULL', '!=')
                  ->fieldOrderBy($field_id, 'value', 'ASC')                   
                  ->execute();

// Attach the field values to the nodes
$nodes = $results['node'];
field_attach_load('node', $nodes, FIELD_LOAD_CURRENT, array('field_id' => $field_id));

// Add a default so the filter is optional
$options = array(
    'Food' => 'Food',
    'Drinks' => 'Drinks',
    );

// Alter the field
$form[$field_id .'_value']['#type'] = 'checkboxes';
$form[$field_id .'_value']['#options'] = $options;

  }
}

Any ideas?