Should fix spurious 'nickname taken' and 'email taken' errors on registration. Form's checks for existing nicks & emails would incorrectly return true on the second lookup due to bad interaction with negative caching.

(was checking $obj !== false but we return null now on negative cache hits, with false for cache misses)

actions/register.php

@@ -280,7 +280,7 @@ class RegisterAction extends Action
     function nicknameExists($nickname)
     {
         $user = User::staticGet('nickname', $nickname);
-        return ($user !== false);
+        return is_object($user);
     }
 
     /**
@@ -300,7 +300,7 @@ class RegisterAction extends Action
             return false;
         }
         $user = User::staticGet('email', $email);
-        return ($user !== false);
+        return is_object($user);
     }
 
     // overrrided to add entry-title class