After converting vb 4.2.5 to phpbb 3.0.11, error in folder "sent messages"

[wonder_wonder]

I have converted vb 4.2.5 to phpbb 3.0.11 (now I need to upgrade to 3.3.11).
After reviewing everything I notice that, if I go to the "Sent messages" folder (private messages), some error lines appear above, they are all the same:

Code: Select all

[phpBB Debug] PHP Warning: in file [ROOT]/includes/ucp/ucp_pm_viewfolder.php on line 180: implode(): Invalid arguments passed
[phpBB Debug] PHP Warning: in file [ROOT]/includes/ucp/ucp_pm_viewfolder.php on line 180: implode(): Invalid arguments passed

The only thing I have seen is that, perhaps the converter is missing or failed in one aspect, the private messages in that folder, the "To" field is blank. Perhaps for that reason, it produces the error.

Any ideas?

Thank you.