ui/pixman: Consistent error handling in qemu_pixman_shareable_free()

qemu_pixman_shareable_free() wraps around either qemu_memfd_free() or
qemu_win32_map_free().  The former reports trouble as error, with
error_report(), then succeeds.  The latter reports it as warning (we
pass it &error_warn), then succeeds.

Change the latter to report as error, too.

Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20250923091000.3180122-10-armbru@redhat.com>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>

ui/qemu-pixman.c

@@ -288,7 +288,10 @@ qemu_pixman_shareable_free(qemu_pixman_shareable handle,
                            void *ptr, size_t size)
 {
 #ifdef WIN32
-    qemu_win32_map_free(ptr, handle, &error_warn);
+    Error *err = NULL;
+
+    qemu_win32_map_free(ptr, handle, &err);
+    error_report_err(err);
 #else
     qemu_memfd_free(ptr, size, handle);
 #endif