[imp] Upgrade errors horde and imp

[tom burkart]

Quoting Jan Schneider <jan at horde.org>:

>> Apr 20 16:54:10 mail httpd: PHP Fatal error:  Call to a member function on a
>> non-object in /home/httpd/html/horde/imp/lib/Block/tree_folders.php  
>>  on line 65
> Looking at the code, I can not see how $imptree at that line could
> *not* be an object.

The only time I have met this is when either (1) not all components  
are at the required revision for it to work together or (2) when the  
database tables are out of sync with the release (ie columns in the  
tables have changed and have not been updated or tables missing, etc).

tom