Test and fix x509_oid functions
diff --git a/library/error.c b/library/error.c
index 9980a91..2ca755c 100644
--- a/library/error.c
+++ b/library/error.c
@@ -655,6 +655,8 @@
 #if defined(POLARSSL_OID_C)
     if( use_ret == -(POLARSSL_ERR_OID_NOT_FOUND) )
         snprintf( buf, buflen, "OID - OID is not found" );
+    if( use_ret == -(POLARSSL_ERR_OID_BUF_TOO_SMALL) )
+        snprintf( buf, buflen, "OID - output buffer is too small" );
 #endif /* POLARSSL_OID_C */
 
 #if defined(POLARSSL_PADLOCK_C)