PMPro Filter member directory multiple select field error

gistfile1.txt

/* The field added via Register Helper. Field works fine in the checkout. */
$fields[] = new PMProRH_Field(
		'category',							// input name, will also be used as meta key
		'select2',								// type of field
		array(
			'label'		=> 'Vælg interesser',		// custom field label
			'options'		=> array("model"=>"Model", "statist"=>"Statist", "actor_unex"=>"Skuespil (uøvet)", "actor_ex"=>"Skuespil (øvet)"),				// input size
			'class'		=> 'category',		// custom class
			'profile'	=> true,			// show in user profile
			'required'	=> true,			// make this field required
			'levels'		=> array(2, 3, 4),	// only level 2, 3 and 4 should have the category field
			'addmember'	=> true,			// Add field to Admin Add member
			'memberslistcsv' => true 	// include field in csv export
		)
	);
  
/* Create filter inputs in sidebar */
<li>
						<strong>Kategori:</strong><br/>
						<?php
						// Set up values to filter for.
						$category = array(
							"model"=>"Model", "statist"=>"Statist", "actor_unex"=>"Skuespil (uøvet)", "actor_ex"=>"Skuespil (øvet)"
						);
						foreach ( $category as $key => $value ) {
							// Check if this value should default to be checked.
							$checked_modifier = '';
							if ( ! empty( $_REQUEST['category'] ) && in_array( $key, $_REQUEST['category'] ) ) {
								$checked_modifier = ' checked';
							}
							// Add checkbox.
							echo '<input type="checkbox" name="category[]" value="' . $key . '"' . $checked_modifier . '><label> ' . $value . '</label><br/>';
						}
						?>
 </li>
 
/* Filter results based on category */
if ( ! empty( $_REQUEST['category'] ) && is_array( $_REQUEST['category'] ) ) {
		$sql_parts['JOIN'] .= " LEFT JOIN $wpdb->usermeta um_category ON um_category.meta_key = 'category' AND u.ID = um_category.user_id ";
		$sql_parts['WHERE'] .= " AND um_category.meta_value in ('" . implode( "','", $_REQUEST['category'] ) . "') ";
	}