Duplicate of Bug #9261.

This might be considered a Duplicate of Ticket #9261.  SystemTask 
tasks might be run before authenticated to the backend server.   
Easiest solution might be to break up tasks that need this extra 
authentication to a simple Task, because they won't be run until a 
user is authenticated to the application.

( ! ) Fatal error: Call to a member function deleteMailbox() on a 
non-object in 
/home/jan/horde-git/imp/lib/LoginTasks/SystemTask/UpgradeFromImp4.php 
on line 82
Call Stack
#        Time        Memory        Function        Location
1        0,0003        668536        {main}( )        ../index.php:0
2        0,4337        12225304        Horde_Block_Layout_View->toHtml( )        ../index.php:52
3        0,4349        12425416        Horde_Block_Collection->getBlock( 'imp', 'summary', 
array ('_refresh_time' => '0'), 0, 0 )        ../View.php:73
4        0,4357        12508616        Horde_Registry->pushApp( 'imp', ??? )        ../Collection.php:145
5        1,3144        27540544        Horde_Core_Factory_LoginTasks->getLoginTasks( 'imp' 
)        ../Registry.php:1228
6        1,3145        27541768        Horde_LoginTasks->__construct( class 
Horde_Core_LoginTasks_Backend_Horde { private $_app = 'imp' } 
)        ../LoginTasks.php:64
7        1,3145        27541848        Horde_LoginTasks->_createTaskList( )        ../LoginTasks.php:77
8        1,3210        28015688        IMP_LoginTasks_SystemTask_UpgradeFromImp4->execute( 
)        ../LoginTasks.php:159
9        1,3211        28015688        IMP_LoginTasks_SystemTask_UpgradeFromImp4->_upgradeExpireImapCache( 
)        ../UpgradeFromImp4.php:30