avoid that run numbers change while selecting policyCosts runs

[orichters]

Purpose of this PR

If you first select the runs for which you want to run policyCosts, and then the reference scenario, the numbers allocated to these runs change, because in the first case, chooseFromList sets the all option as Nr. 1, while in the second case you are only allowed to select a single run, so the all option does not exist. Add some pseudo run there to make sure the runs keep the same number.

Type of change

• [x] Minor bug fix

Checklist:

• [x] My code follows the coding etiquette
• [x] I performed a self-review of my own code
• [x] I explained my changes within the PR, particularly in hard-to-understand areas
• [x] All automated model tests pass (FAIL 0 in the output of make test)