Undefined index when enabling or disabling hosts in a host group

When I try to enable or disable a host group, an undefined index error appears:

Undefined index: host [ in /opt/lampp/htdocs/zabbix/trunk/frontends/php/hostgroups.php:218]

Regression, broken by:
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r45676 | sasha | 2014-05-20 15:39:29 +0300 (Tue, 20 May 2014) | 1 line

..F....... ZBX-5567 refactored Configuration -> Host groups screen
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