if (NS_FAILED(rv) || pPref == nsnull)
if (NS_FAILED(rv) || !pPref)
nsresult DIR_GetDirServers(){    nsresult rv = NS_OK;    NS_WITH_SERVICE(nsIPref, pPref, kPrefCID, &rv);     if (NS_FAILED(rv) || pPref == nsnull) 		return NS_ERROR_FAILURE;	if (!dir_ServerList)	{		/* we need to build the DIR_Server list */ 		rv = DIR_GetServerPreferences(&dir_ServerList);		/* Register the preference call back if necessary. */		if (NS_SUCCEEDED(rv) && (!dir_ServerPrefCallbackRegistered))		{			dir_ServerPrefCallbackRegistered = PR_TRUE;        	pPref->RegisterCallback(PREF_LDAP_SERVER_TREE_NAME, dir_ServerPrefCallback, nsnull);		}	}	return rv;}