[BUG] - Model errors when a storage asset is investable==false but storage_method_energy==true

[gnawin]

Description

Model errors when a storage asset is investable==false but storage_method_energy==true.

This setup triggers an error in this part of the objective function,

$$\begin{aligned} \sum_{a \in \mathcal{A}^{\text{se}} } p^{\text{inv cost energy}}_{a} \cdot p^{\text{energy}}_{a} \cdot v^{\text{inv energy}}_{a} \end{aligned}$$

because $v^{\text{inv energy}}_{a}$ is only defined for $a \in Ase \cap Ai$, so it errors when $a \in Ase, a \notin Ai$

A minor issue is that the documentation needs to be changed accordingly:

• objective function

Reproduction steps

1. Change input data 'test/inputs/Norse'
2. For `Asgard_Battery`: set `investable==false` and `storage_method_energy==true`.
3. [Specific error message]

ERROR: KeyError: key :Asgard_Battery not found

### Logs

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### OS

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