Invalid argument supplied for foreach() in viewfield.module on line 278

warning: Invalid argument supplied for foreach() in viewfield/viewfield.module on line 278.
Backtrace: _viewfield_potential_references(...)[viewfield.module:211] <=viewfield_select_process(...)[form.inc:1055] <=_form_builder_handle_input_element(...)[form.inc:881] <=form_builder(...)[form.inc:922] <=form_builder(...)[form.inc:922] <=form_builder(...)[form.inc:399] <=drupal_process_form(...)[form.inc:119] <=drupal_get_form(...)[node.pages.inc:15] <=node_page_edit(...)[:] <=call_user_func_array(...)[menu.inc:348] <=menu_execute_active_handler(Array)[index.php:18] <=index.php