Invalidate captcha after reg

git-svn-id: file:///svn/phpbb/branches/phpBB-3_0_0@10417 89ea8834-ac86-4346-8a33-228a782c2dd0

phpBB/includes/ucp/ucp_register.php

@@ -334,7 +334,7 @@ function main($id, $mode)
 				}
 
 				// Okay, captcha, your job is done.
-				if (isset($captcha))
+				if ($config['enable_confirm'] && isset($captcha))
 				{
 					$captcha->reset();
 				}