Not using multisite but get frequent error: Invalid argument Domain.php

[sonicthoughts]

My understanding is that Domain.php is used for multisite but I keep getting an error:
Warning: Invalid argument supplied for foreach() in civicrm_api3_domain_get() (line 59 of /home/xxx/public_html/beta/sites/all/modules/civicrm/api/v3/Domain.php).

This happens on many management URLs with admin rights - mostly related to extensions management.  here is a backtrace...

Location   https://beta.xxx.com/civicrm/admin/extensions?reset=1&action=browse
Referrer   https://beta.xxx.com/civicrm/admin/extensions?action=add&id=com.pogstone.fancytokens&key=com.pogstone.fancytokens
Message   Warning: Invalid argument supplied for foreach() in civicrm_api3_domain_get() (line 59 of /home/xxx/public_html/beta/sites/all/modules/civicrm/api/v3/Domain.php).
Severity   warning

Operations   
debug_backtrace()
Id   Function   Location
Id   Function   Location
#28   eval ( )   /sites/all/modules/watchdog_debug/watchdog_debug.module : 108
#27   watchdog_debug_watchdog ( Array )   
#26   call_user_func_array ( Array )   /includes/module.inc : 866
#25   module_invoke ( Array )   /includes/bootstrap.inc : 1735
#24   watchdog ( Array )   /sites/all/modules/devel/devel.module : 750
#23   backtrace_error_handler ( Array )   /sites/all/modules/civicrm/api/v3/Domain.php : 59
#22   civicrm_api3_domain_get ( Array )   /sites/all/modules/civicrm/api/api.php : 87
#21   civicrm_api ( Array )   /sites/all/modules/civicrm/api/v3/Generic.php : 138
#20   civicrm_api3_generic_getcount ( Array )   /sites/all/modules/civicrm/api/api.php : 82
#19   civicrm_api ( Array )   /sites/default/files/civicrm/extensions/eu.tttp.setting-1.2/setting.php : 43
#18   setting_civicrm_navigationMenu ( Array )   /sites/all/modules/civicrm/CRM/Utils/Hook.php : 148
#17   runHooks ( Array )   /sites/all/modules/civicrm/CRM/Utils/Hook/Drupal.php : 67
#16   invoke ( Array )   /sites/all/modules/civicrm/CRM/Utils/Hook.php : 809
#15   navigationMenu ( Array )   /sites/all/modules/civicrm/CRM/Core/BAO/Navigation.php : 325
#14   buildNavigation ( )   /sites/all/modules/civicrm/CRM/Core/BAO/Navigation.php : 596
#13   createNavigation ( Array )   /sites/all/modules/civicrm/CRM/Core/Smarty/plugins/function.crmNavigationMenu.php : 55
#12   smarty_function_crmNavigationMenu ( Array )   /sites/default/files/civicrm/templates_c/en_US/%%06/069/0693F89E%%drupal.tpl.php : 24
#11   include ( Array )   /sites/all/modules/civicrm/packages/Smarty/Smarty.class.php : 1264
#10   fetch ( Array )   /sites/all/modules/civicrm/CRM/Core/Smarty.php : 194
#9   fetch ( Array )   /sites/all/modules/civicrm/CRM/Core/Page.php : 207
#8   run ( )   /sites/all/modules/civicrm/CRM/Core/Page/Basic.php : 185
#7   run ( )   /sites/all/modules/civicrm/CRM/Admin/Page/Extensions.php : 127
#6   run ( Array )   /sites/all/modules/civicrm/CRM/Core/Invoke.php : 323
#5   runItem ( Array )   /sites/all/modules/civicrm/CRM/Core/Invoke.php : 72
#4   _invoke ( Array )   /sites/all/modules/civicrm/CRM/Core/Invoke.php : 52
#3   invoke ( Array )   /sites/all/modules/civicrm/drupal/civicrm.module : 456
#2   civicrm_invoke ( Array )   
#1   call_user_func_array ( Array )   /includes/menu.inc : 517
#0   menu_execute_active_handler ( )   /index.php : 21