weight_and_balance: fix fuel loading approach

Bug Report

Description

It seems like weight_and_balance aborts if less fuel is needed during the mission and with this less tanks are required/needs to be filled than given in the aircraft_exchange file:

But this shouldn't be a problem.

Steps to Reproduce

1. Use the project given here: UNICADOworkflow_2025-04-14_10-06-31_20_Failed_execution_UNICADO-SMR-180-TF.zip
2. Execute weight_and_balance module to this project

Expected Behavior

If a tank is available but not used during mission, weight_and_balance should assume 0 kg of fuel in this tank.

Environment

• OS: Windows 10
• Version/Branch: v0.5.0

Additional Context

This bug could be reproduced by using the status of aircraft_design repo in commit 28dd0407 and using the config file for wing_design given in the config_files folder of the attached project (higher aspect ratio and higher taper_ratio) running in the workflow