more useful error message where there is nothing to choose from

fulcrm_shoppingcart.module

@@ -716,8 +716,11 @@ function fulcrm_shoppingcart_buy_eventbookingtype_form( $form, &$form_state, $pe
     }
 
     $choices = false;
+    $zero_options = false;
     foreach ( $form[ 'eventslots' ] as $eventpart_id => $eventpart_form ) {
-        if ( count( $eventpart_form[ '#options' ] ) == 1 ) {
+        if ( count( $eventpart_form[ '#options' ] ) == 0 ) {
+            $zero_options = true;
+        } else if ( count( $eventpart_form[ '#options' ] ) == 1 ) {
             foreach ( $eventpart_form[ '#options' ] as $option_key => $option_value )
                 $form[ 'eventslots' ][ $eventpart_id ][ '#default_value' ] = $option_key;
         } else {
@@ -725,6 +728,10 @@ function fulcrm_shoppingcart_buy_eventbookingtype_form( $form, &$form_state, $pe
         }
     }
 
+    if ( $zero_options ) {
+        drupal_set_message(t('Unfortunately it looks like some of the choices for this type of ticket are completely sold out.'), 'error', FALSE);
+    }
+
     if ( $choices ) {
         $form[ 'ticket_for_persons' ][ '#type' ] = 'radios';
         if ( count( $form[ 'ticket_for_persons' ][ '#options' ] ) == 1 ) {
@@ -752,6 +759,11 @@ function fulcrm_shoppingcart_buy_eventbookingtype_form( $form, &$form_state, $pe
                                             '#submit' => array( 'fulcrm_shoppingcart_buy_eventbookingtype_form_submit' ),
                                             );
 
+    if ( $zero_options ) {
+        $form[ 'actions' ][ 'submit' ][ '#disabled' ] = true;
+        $form[ 'actions' ][ 'submit' ][ '#value' ] = t('Sold Out');
+    }
+
     return $form;
 }