View based on activity generates mysql error for any user other than admin

I created a simple view that shows the user activity. It works for admin but any other user causes the following mysql error:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AND (activity_messages.nid IS NULL OR (na.grant_view >= 1 AND ((na.gid = 0 AND n'

Here's the full query:

SELECT DISTINCT (
activity_messages.amid
) AS amid, activity_messages.everyone_message AS activity_messages_everyone_message, activity_messages.author_message AS activity_messages_author_message, activity_messages.uid AS activity_messages_uid, activity_messages.created AS activity_messages_created, DATE_FORMAT( (
FROM_UNIXTIME( activity_messages.created ) + INTERVAL -14400
SECOND ) ,  '%Y%m%d%H%i'
) AS activity_messages_created_minute
FROM activity_messages activity_messages
LEFT JOIN node_access na ON na.nid = activity_messages.nid
AND activity_messages.type =  'node'
WHERE (

AND (
activity_messages.nid IS NULL 
OR (
na.grant_view >=1
AND (
(
na.gid =0
AND na.realm =  'all'
)
OR (
na.gid =0
AND na.realm =  'og_public'
)
OR (
na.gid =115
AND na.realm =  'og_admin'
)
)
)
)
)
ORDER BY activity_messages_created_minute DESC 
LIMIT 0 , 20

Notice that the WHERE clause starts with AND.

I modified line 411 in the latest release of activity.module as follows:

//      $return['where'] = " AND ($primary_table.nid IS NULL OR (" . $node_access . "))";
      $return['where'] = " ($primary_table.nid IS NULL OR (" . $node_access . "))";

This fixed the error but, honestly, I have no idea what I'm doing so I don't think this is correct fix. Does anyone else understand what's happening here?