Bug#992614: Fails to open 1-bit, black and white, indexed BMP files

[mason1920]

Package: gimp
Version: 2.10.22-4

Reproduce:
0. Create a new image
1. Set the image mode to indexed, 1-bit, black and white
(Image→Mode→Indexed...→Use black and white (1-bit) palette)
2. Export image in the Windows BMP image format
3. Open the exported file

Previously, in the GIMP 2.10.8-2 available in Debian Buster, the issue of not being able to open BMP files created by itself was non-existent. It is also worth noting that the BMP created by both versions can be opened by 2.10.8-2, but not by 2.10.22-4, so it's not an issue with the exporting method changing.