py/objstr: Allow to compile with obj-repr D, and unicode disabled.
diff --git a/py/objstr.c b/py/objstr.c
index 1d2a280..e758dd0 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -2135,7 +2135,7 @@
 
 #if !MICROPY_PY_BUILTINS_STR_UNICODE
 STATIC mp_obj_t str_it_iternext(mp_obj_t self_in) {
-    mp_obj_str8_it_t *self = self_in;
+    mp_obj_str8_it_t *self = MP_OBJ_TO_PTR(self_in);
     GET_STR_DATA_LEN(self->str, str, len);
     if (self->cur < len) {
         mp_obj_t o_out = mp_obj_new_str((const char*)str + self->cur, 1, true);
@@ -2153,7 +2153,7 @@
     o->iternext = str_it_iternext;
     o->str = str;
     o->cur = 0;
-    return o;
+    return MP_OBJ_FROM_PTR(o);
 }
 #endif