py/{modbuiltins,repl}: Start qstr probing from after empty qstr.

The list of qstrs starts with MP_QSTR_NULL followed by MP_QSTR_, and these
should never appear in dir() or REPL tab completion, so skip them.

py/modbuiltins.c

@@ -186,7 +186,7 @@ STATIC mp_obj_t mp_builtin_dir(size_t n_args, const mp_obj_t *args) {
         // Make a list of names in the given object
         // Implemented by probing all possible qstrs with mp_load_method_maybe
         size_t nqstr = QSTR_TOTAL();
-        for (size_t i = 1; i < nqstr; ++i) {
+        for (size_t i = MP_QSTR_ + 1; i < nqstr; ++i) {
             mp_obj_t dest[2];
             mp_load_method_maybe(args[0], i, dest);
             if (dest[0] != MP_OBJ_NULL) {

py/repl.c

@@ -176,7 +176,7 @@ size_t mp_repl_autocomplete(const char *str, size_t len, const mp_print_t *print
             const char *match_str = NULL;
             size_t match_len = 0;
             qstr q_first = 0, q_last;
-            for (qstr q = 1; q < nqstr; ++q) {
+            for (qstr q = MP_QSTR_ + 1; q < nqstr; ++q) {
                 size_t d_len;
                 const char *d_str = (const char*)qstr_data(q, &d_len);
                 if (s_len <= d_len && strncmp(s_start, d_str, s_len) == 0) {