The chord calculation has a bug

[burmist-git]

Describe the bug
The chord calculation has a bug.
It does not account for non-physical solutions in the chord calculation for points outside the mirror. This is important for fitting with the central hole in the mirror, or when accounting for camera shadowing. (MR: Muon fit chord length fix #2803 )

To Reproduce
The code to reproduce this error is here:
https://github.com/burmist-git/ctapipe_run_dir/blob/master/muons_chord_D.ipynb

Expected behavior
The values from the side are non-physical.

Supporting information
#2760 (comment)

Additional context

Filtering out non-physical solutions using this inequality equation (equation 7, page 3 from https://doi.org/10.1016/0927-6505(94)90012-4):