canon - How do I get my EOS M to release the shutter with an adapted manual lens?

I have a Canon FD-mount lens and a Nikon pre-AI lens, with respective adapters.

I attach the FD lens to my EOS M, set the camera to M or Av mode, and the aperture is fixed at 00. When I press the shutter button, it doesn't fire.

How do I use these vintage lens on an EOS M?