Problems seem to require a parameter tuple/vector

[isaacsas]

This gives an error:

using Catalyst, DiffEqBase, OrdinaryDiffEq
rn = @reaction_network begin
           exp(-(t-5)^2), 0 --> S
           1.0, S --> 0
       end 
oprob = ODEProblem(rn, [0.0], (0.0,20.0))

Seems we haven't setup the problem generation to allow for no parameters when skipping conversion from a system. (Probably we should fix this in MT, but I'm opening this here since it is a Catalyst issue and we might move ReactionSystems here eventually...)

[TorkelE]

Will have a look at this tomorrow, hopefully an easy fix.

[isaacsas]

Yeah, probably just need to default p to be a DiffEqBase.NullParameters and then avoid parameters calculations in that case.

[isaacsas]

Closed by SciML/ModelingToolkit.jl#542