extmod/vfs_posix_file: Ensure file object has safe default fd.

If file open fails the object will have fd = -1 (closed).

Signed-off-by: Andrew Leech <[email protected]>

extmod/vfs_posix_file.c

@@ -64,6 +64,7 @@ STATIC void vfs_posix_file_print(const mp_print_t *print, mp_obj_t self_in, mp_p
 
 mp_obj_t mp_vfs_posix_file_open(const mp_obj_type_t *type, mp_obj_t file_in, mp_obj_t mode_in) {
     mp_obj_vfs_posix_file_t *o = m_new_obj_with_finaliser(mp_obj_vfs_posix_file_t);
+    o->fd = -1;   // In case open() fails below, initialise this as a "closed" file object.
     const char *mode_s = mp_obj_str_get_str(mode_in);
 
     int mode_rw = 0, mode_x = 0;