bug#68339: [patch] Set the IME window font to an appropriate size

> From: dANiuu zHaO <[email protected]>
> Date: Sun, 2 Aug 2026 23:27:31 +0800
> Cc: [email protected]
> 
> You were right. I only needed to build it once locally and it worked perfectly — exactly as you described, with no
> errors at all. There's a new patch and a GIF attached to demonstrate my current work.
> Everything works fine on my local machine, but it will likely need more testing from others. Lastly, thank you for
> your guidance — without it, it would have taken me much longer to figure out the root cause.

Yes, more testing is a good idea.

> Finally, I agree to sign the copyright-assignment agreement.

Thanks, form sent off-list.

> +	  face = FACE_FROM_ID (f, lookup_basic_face (w, f, DEFAULT_FACE_ID));
> +	  GetObjectW (FONT_HANDLE (face->font), sizeof (lf), &lf);

Please add the fallback here, in case something goes wrong.
Specifically, if either 'face' or face->font is NULL, we should use
FRAME_FONT as fallback.

Also, please use FACE_FROM_ID_OR_NULL instead of FACE_FROM_ID, because
the latter will hit assert violation if the result is NULL, whereas we
want to handle that ourselves here.