py: Fix mp_obj_print() to work when Python streams are not used.

py/obj.c

@@ -72,14 +72,16 @@ void mp_obj_print_helper(void (*print)(void *env, const char *fmt, ...), void *e
 }
 
 void mp_obj_print(mp_obj_t o_in, mp_print_kind_t kind) {
+#if MICROPY_PY_IO
     // defined per port; type of these is irrelevant, just need pointer
     extern mp_uint_t mp_sys_stdout_obj;
-
     pfenv_t pfenv;
     pfenv.data = &mp_sys_stdout_obj;
     pfenv.print_strn = (void (*)(void *, const char *, mp_uint_t))mp_stream_write;
-
     mp_obj_print_helper((void (*)(void *env, const char *fmt, ...))pfenv_printf, &pfenv, o_in, kind);
+#else
+    mp_obj_print_helper(printf_wrapper, NULL, o_in, kind);
+#endif
 }
 
 // helper function to print an exception with traceback