Panic on ~main~ `second_new_tranching_approach` in this model

## Describe the bug

This model panics halfway through the simulation. The model is very similar to simple_modified, just has higher capex costs for one process. Output I see

[simple_modified_withpanic.zip](https://github.com/user-attachments/files/29805652/simple_modified_withpanic.zip)

is:

root@4c09da989d89:/workspaces/MUSE_2.0# cargo run run examples/simple_modified --overwrite --debug-model
Compiling muse2 v2.1.0 (/workspaces/MUSE_2.0)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 22.01s
Running `target/debug/muse2 run examples/simple_modified --overwrite --debug-model`
[14:27:02 INFO muse2::cli] Starting MUSE2 v2.1.0
[14:27:02 WARN muse2::model::parameters] !!! You've enabled the please_give_me_broken_results option. !!!
I see you like to live dangerously 😈. This option should ONLY be used by developers as it can cause peculiar behaviour that breaks things. NEVER enable it for results you actually care about or want to publish. You have been warned!
[14:27:02 INFO muse2::cli] Loaded model from /workspaces/MUSE_2.0/examples/simple_modified
[14:27:02 INFO muse2::cli] Output folder: muse2_results/simple_modified
[14:27:02 WARN muse2::cli] Output folder will be overwritten
[14:27:02 INFO muse2::simulation] Milestone year: 2020
[14:27:02 INFO muse2::simulation] Running dispatch optimisation...
[14:27:02 INFO muse2::simulation] Milestone year: 2021
[14:27:02 INFO muse2::simulation] Running agent investment...
[14:27:02 INFO muse2::simulation] Running dispatch optimisation...
[14:27:02 INFO muse2::simulation] Max ironing out iterations (1) reached
[14:27:02 INFO muse2::simulation] Running final dispatch optimisation for year 2021...
[14:27:02 INFO muse2::simulation] Milestone year: 2022
[14:27:02 INFO muse2::simulation] Running agent investment...
[14:27:03 INFO muse2::simulation] Running dispatch optimisation...
[14:27:03 INFO muse2::simulation] Max ironing out iterations (1) reached
[14:27:03 INFO muse2::simulation] Running final dispatch optimisation for year 2022...
[14:27:03 INFO muse2::simulation] Milestone year: 2023
[14:27:03 INFO muse2::simulation] Running agent investment...
[14:27:03 INFO muse2::simulation] Running dispatch optimisation...
[14:27:03 INFO muse2::simulation] Max ironing out iterations (1) reached
[14:27:03 INFO muse2::simulation] Running final dispatch optimisation for year 2023...
[14:27:03 INFO muse2::simulation] Milestone year: 2024
[14:27:03 INFO muse2::simulation] Running agent investment...
[14:27:03 INFO muse2::simulation] Running dispatch optimisation...
[14:27:03 INFO muse2::simulation] Max ironing out iterations (1) reached
[14:27:03 INFO muse2::simulation] Running final dispatch optimisation for year 2024...
[14:27:03 INFO muse2::simulation] Milestone year: 2025
[14:27:03 INFO muse2::simulation] Running agent investment...
[14:27:03 INFO muse2::simulation] Running dispatch optimisation...
[14:27:03 INFO muse2::simulation] Max ironing out iterations (1) reached
[14:27:03 INFO muse2::simulation] Running final dispatch optimisation for year 2025...
[14:27:03 INFO muse2::simulation] Milestone year: 2026
[14:27:03 INFO muse2::simulation] Running agent investment...
[14:27:04 INFO muse2::simulation] Running dispatch optimisation...
[14:27:04 INFO muse2::simulation] Max ironing out iterations (1) reached
[14:27:04 INFO muse2::simulation] Running final dispatch optimisation for year 2026...
[14:27:04 INFO muse2::simulation] Milestone year: 2027
[14:27:04 INFO muse2::simulation] Running agent investment...
[14:27:04 INFO muse2::simulation] Running dispatch optimisation...
[14:27:04 INFO muse2::simulation] Max ironing out iterations (1) reached
[14:27:04 INFO muse2::simulation] Running final dispatch optimisation for year 2027...
[14:27:04 INFO muse2::simulation] Milestone year: 2028
[14:27:04 INFO muse2::simulation] Running agent investment...

thread 'main' (147140) panicked at /rustc/31fca3adb283cc9dfd56b49cdee9a96eb9c96ffd/library/core/src/slice/sort/shared/smallsort.rs:860:5:
user-provided comparison function does not correctly implement a total order
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

## To Reproduce

Run the attached model.

## Expected behavior

A clearly described error, or handling whatever is going on here.