Simulation wizard: constant substance concentration is not added to boundary conditions from simulation template

[leendertvanwolfswinkel]

How to reproduce:

• Start a new simulation.
  • Model: Demo model Assen Loon Close side-view by clicking x #29
  • Simulation template: demo 3
• Include:
  • Substances
  • Boundary conditions
• Define a substance "BC", units "%"
• On the boundary conditions page, fill in 100 for "BC (1D)"
• Start the simulation
• The boundary conditions JSON (downloaded via the https://api.3di.live/v3/simulations/{simulation_id}/events/boundaryconditions/file/ endpoint) does not include a time series for substance concentrations