Permissions failure

This is my first bug report as a drupal user, I hope I put it in the right place.

I am using drupal 5 with Event module and basicEvent content. The configuration of my drupal has many other modules, such as domain to handle multisite, and an online shop (ubercart). The bug is quite huge, which make me think that it's the interaction between all modules that makes it appear.

I checked in the Administration (basicevent permission) the edit own event part. But the fact is I could edit any event node, and even delete them. Then I looked at basicevent_access function and it looks like :

if (user_access('edit own events') && ($user->uid == $node->uid)) {
        return TRUE;
      }

I changed it into

if (user_access('edit own events') && ($user->uid == $node->uid)) {
        return TRUE;
      }
      else
      	return FALSE;

And now it works. The source of the bug might the multiple node access patch, thought I don't see how it can be.

Why not just returning the result of the condition evaluation ?