bug#81585: 31.0.91 and 32.0.50; Crash on macos hiding header-line with pixel-scroll-precision-mode

> Could you try reproducing this on Emacs 30 as well?

Reproduced in Emacs 30.

I had trouble building Emacs 30 (segfault in a bootstrapping step),
so I downloaded a built version from emacsformacos . com

In GNU Emacs 30.2 (build 2, x86_64-apple-darwin20.6.0, NS appkit-2022.70
Version 11.7.11 (Build 20G1443)) of 2026-07-25 built on builder11.lan
Repository revision: 1735bab5b34f9b81dcb9b77552b331be99c01845
Repository branch: HEAD
Windowing system distributor 'Apple', version 10.3.2575
System Description:  macOS 15.7.8

Part of traceback from the macos crash reporter:

9   libsystem_platform.dylib      	    0x7ff81bb0a31d _sigtramp + 29
10  AppKit                        	    0x7ff81f75c3b7 NSColorSetWithFillAndStroke + 163
11  Emacs-x86_64-11               	       0x10cdaadc7 -[EmacsView copyRect:to:] + 551
12  Emacs-x86_64-11               	       0x10cdb4272 ns_scroll_run + 418
13  Emacs-x86_64-11               	       0x10cb69624 update_window + 6164
14  Emacs-x86_64-11               	       0x10cb69a15 update_window_tree + 117
15  Emacs-x86_64-11               	       0x10cb67c57 update_frame + 231


Corwin