Error message

• Notice: Trying to get property of non-object in user_access() (line 790 of /home/feathers/webfeathers.com/drupal/modules/user/user.module).
• Notice: Trying to get property of non-object in user_access() (line 802 of /home/feathers/webfeathers.com/drupal/modules/user/user.module).
• Notice: Trying to get property of non-object in user_access() (line 803 of /home/feathers/webfeathers.com/drupal/modules/user/user.module).
• Notice: Trying to get property of non-object in user_access() (line 809 of /home/feathers/webfeathers.com/drupal/modules/user/user.module).
• Notice: Trying to get property of non-object in user_access() (line 812 of /home/feathers/webfeathers.com/drupal/modules/user/user.module).
• Notice: Trying to get property of non-object in twitter_twitter_accounts() (line 257 of /home/feathers/webfeathers.com/drupal/sites/all/modules/twitter/twitter.module).