Warnings on boot if gonio axes values are not set

[GDYendell]

If they are set then it works fine because the fetch returns a float.

Failed to get detector/api/1.8.0/config/phi_increment:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/kappa_start:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/phi_start:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/chi_increment:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/chi_start:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/kappa_increment:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/omega_start:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/omega_increment:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/two_theta_increment:
TypeError float() argument must be a string or a real number, not 'NoneType'
Failed to get detector/api/1.8.0/config/two_theta_start:
TypeError float() argument must be a string or a real number, not 'NoneType'

Check if this happens with a real detector. If the real detector returns None, then we need to handle it correctly. If it is just the simulator then that should be fixed.

Steps To Reproduce

With sim

1. Start tickit simulator
2. Start IOC

or with real detector

1. Re-initialise the detector
2. Check what values these parameters have with curl
   • e.g. curl -v http://ixx-eiger01/detector/api/1.8.0/config/phi_start
3. Start IOC

Acceptance Criteria

• No warnings on boot

[GDYendell]

I don't seem to be able to reproduce this with the sim currently...