ui/pixman: Fix crash in qemu_pixman_shareable_free()

Reported-by: Bernhard Beschow <shentey@gmail.com>
Fixes: b296b29d34 (ui/pixman: Consistent error handling in qemu_pixman_shareable_free())
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20251013112102.2396012-1-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Bernhard Beschow <shentey@gmail.com>

ui/qemu-pixman.c

@@ -291,7 +291,9 @@ qemu_pixman_shareable_free(qemu_pixman_shareable handle,
     Error *err = NULL;
 
     qemu_win32_map_free(ptr, handle, &err);
-    error_report_err(err);
+    if (err) {
+        error_report_err(err);
+    }
 #else
     qemu_memfd_free(ptr, size, handle);
 #endif