round_corner filter fails for bmp images

[vgrigoruk]

Example:

http://localhost:8000/unsafe/200x200/filters:format(jpg):round_corner(50)/https://www.janome.com/inspire/Embroidery/penguin-bmp-design-from-digitizer-10000/penguin-bmp-design-from-digitizer-10000/dig10k_penguin.bmp

Error:

{"message":"vips_colourspace: no known route from 'multiband' to 'srgb'","status":406}