fix(fms): fix uplink crash for airway terminations not on airways

[BlueberryKing]

Fixes #[issue_no]

Summary of Changes

Due to navigation database disagreements between SimBrief and MSFS, it could happen that SimBrief produces route segments whose terminations still exist in the MSFS navdata, but are no longer on the expected airway. This case is now handled more gracefully.

Screenshots (if necessary)

References

Additional context

Discord username (if different from GitHub):

Testing instructions

• Produce a route on SimBrief with an outdated AIRAC cycle
• Import the route using INIT REQUEST
• There should be scratchpad messages such as AWY/WPT MISMATCH or INTERNAL ERROR, but most of the flightplan should still uplink, albeit with discontinuities between waypoints.

How to download the PR for QA

Every new commit to this PR will cause new A32NX and A380X artifacts to be created, built, and uploaded.

1. Make sure you are signed in to GitHub
2. Click on the Checks tab on the PR
3. On the left side, find and click on the PR Build tab
4. Click on either flybywire-aircraft-a320-neo or flybywire-aircraft-a380-842 download link at the bottom of the page