SAM crashes when REopt optimization energy rates include kWh/kW units

Describe the bug

When the maximum usage units on the Electricity Rates page are "kWh/kW" in the energy rates table, running the REopt optimization from the Battery Cell and System page causes SAM to crash.

For examples with kWh/kW units, see Duke Energy Large General Servcice (LGS) rates.

To Reproduce

Steps to reproduce the behavior:

1. Open example file kwh-kw-max-usage-units.zip
2. Note kWh/kW units in energy rate table on Electricity Rates page.
3. On Battery Cell and System page, click Get size and dispatch.
4. SAM crashes.

Expected behavior

REopt optimization should either run work kWh/kW units, or SAM should display an error message like "REopt optmization does not support kWh/kW maximum usage units for energy rates."

Operating System and Version

SAM 2025.4.16 r1 for Windows.

Additional context

This seems like it should be handled as an error by Line 97 of try_get_rate_structure() in cmod_utilityrate5_eqns.cpp:

But perhaps this REopt error handling issue is preventing the error from being displayed correctly: https://github.com/NatLabRockies/SAM/issues/2131.

See also:

• REopt time series sell rates: https://github.com/NatLabRockies/SAM/issues/2119
• Other unique rate components from Duke Energy: https://github.com/NatLabRockies/SAM/issues/615

Reproduce the crash with kwh-kw-max-usage-units.zip by using Get size and dispatch on the Battery Cell and System page. Start in cmod_utilityrate5_eqns.cpp at try_get_rate_structure(), especially line 97, and review the REopt error-handling context in issue 2131. Done means kWh/kW rates no longer crash SAM and either optimize successfully or show an error message.