Waypoint too close to cellbox boundary crashes smoothing

[hjabbot]

Describe the bug
Smoothing crashes when there's a waypoint very close to a cellbox boundary. It does not crash when the waypoint is on the boundary though.

To Reproduce
Set a waypoint very close to a cellbox edge. Specifically, I put a waypoint with longitude -52.499999 with a mesh that had a cellbox border at -52.5

Screenshots & Files

[08-10-24 15:18:23 :INFO    ] - optimise_routes 1.0.0
[08-10-24 15:18:23 :INFO    ] - Initialising Route Planner
[08-10-24 15:18:23 :INFO    ] - Calculating Dijkstra routes
[08-10-24 15:18:23 :INFO    ] - ============= Dijkstra Route Creation ============
[08-10-24 15:18:23 :INFO    ] -  - Objective = traveltime
[08-10-24 15:18:23 :INFO    ] - --- Processing Source Waypoint = WP_A
[08-10-24 15:18:23 :INFO    ] - Destination waypoint: WP_B
[08-10-24 15:18:24 :INFO    ] - Dijkstra routing complete...
[08-10-24 15:18:24 :INFO    ] - Timed call to compute_routes took 0.575328 seconds
[08-10-24 15:18:24 :INFO    ] - 	Outputting dijkstra path to ow_nu_sd5_nsf_escf.route_dijkstra.json
[08-10-24 15:18:24 :INFO    ] - Calculating smoothed routes
[08-10-24 15:18:24 :INFO    ] - ========= Determining Smoothed Routes ===========
[08-10-24 15:18:24 :INFO    ] - --- Smoothing Route - WP_A to WP_B
Traceback (most recent call last):
  File "/home/habbot/Documents/Work/BAS/repos/sdadt/venv_dev/bin/optimise_routes", line 8, in <module>
    sys.exit(optimise_routes_cli())
             ^^^^^^^^^^^^^^^^^^^^^
  File "/home/habbot/Documents/Work/BAS/repos/sdadt/PolarRoute/polar_route/utils.py", line 238, in wrapper
    res = func(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^
  File "/home/habbot/Documents/Work/BAS/repos/sdadt/PolarRoute/polar_route/cli.py", line 202, in optimise_routes_cli
    smoothed_routes = rp.compute_smoothed_routes()
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/habbot/Documents/Work/BAS/repos/sdadt/PolarRoute/polar_route/utils.py", line 238, in wrapper
    res = func(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^
  File "/home/habbot/Documents/Work/BAS/repos/sdadt/PolarRoute/polar_route/route_planner/route_planner.py", line 700, in compute_smoothed_routes
    sf.forward()
  File "/home/habbot/Documents/Work/BAS/repos/sdadt/PolarRoute/polar_route/route_planner/crossing_smoothing.py", line 1301, in forward
    self.remove(ii) #Removing app
    ^^^^^^^^^^^^^^^
  File "/home/habbot/Documents/Work/BAS/repos/sdadt/PolarRoute/polar_route/route_planner/crossing_smoothing.py", line 687, in remove
    self.aps.pop(index)