Migration attempt fails: Call to a member function capability() on a non-object

Symptoms

When attempting to migrate a reseller's subscription without migrating the reseller itself, the attempt fails with the following errors:

PHP Notice: Trying to get property of non-object; File: /usr/local/psa/admin/plib/backup/Conflicts/PleskDataManager.php, Line: 173
PHP Notice: Undefined index: xxx.xxx.xxx.xxx; File: /usr/local/psa/admin/plib/backup/Conflicts/PleskDataManager.php, Line: 180
PHP Fatal error:  Call to a member function capability() on a non-object in /usr/local/psa/admin/plib/backup/Conflicts/Resolver/UnfitSettingsResolver.php on line 292

(Where <xxx.xxx.xxx.xxx> is the IP address).

Additionally, the following error can be found in /var/log/plesk/panel.log when debug mode is enabled:

... 
DEBUG [dbquery] [64] SQL: SELECT `IP_Addresses`.* FROM `IP_Addresses` AS `IP_Addresses` WHERE (`serviceNodeId` = '')
...
Debug: Unable to get service node IP for phosting on subscription.tld

(Where <subscription.tld> is the affected subscription name).

Cause

This is Plesk bug with ID #PPPM-1754 that was fixed in Plesk 12.0.18 MU#9

Resolution

Install the latest micro-updates .