Fix solvers failed on OOP problem

[ErikQQY]

using SimpleDiffEq
f(u,p,t) = 1.01*u
u0=1/2
tspan = (0.0,1.0)
prob = ODEProblem(f,u0,tspan)
sol = solve(prob, SimpleTsit5(), dt=0.01)

would cause errors:

ERROR: MethodError: no method matching simpletsit5_init(::ODEFunction{false, SciMLBase.AutoSpecialize, typeof(f), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, ::Bool, ::Float64, ::Float64, ::Float64, ::SciMLBase.NullParameters)
An arithmetic operation was performed on a NullParameters object. This means no parameters were passed
into the AbstractSciMLProblem (e.x.: ODEProblem) but the parameters object `p` was used in an arithmeticexpression. Two common reasons for this issue are:

1. Forgetting to pass parameters into the problem constructor. For example, `ODEProblem(f,u0,tspan)` should
be `ODEProblem(f,u0,tspan,p)` in order to use parameters.

2. Using the wrong function signature. For example, with `ODEProblem`s the function signature is always
`f(du,u,p,t)` for the in-place form or `f(u,p,t)` for the out-of-place form. Note that the `p` argument
will always be in the function signature reguardless of if the problem is defined with parameters!

Closest candidates are:
  simpletsit5_init(::F, ::Bool, ::S, ::T, ::T, ::P) where {F, P, T, S<:(AbstractArray{T})}
   @ SimpleDiffEq D:\Julia\.julia\packages\SimpleDiffEq\tY7zU\src\tsit5\tsit5.jl:58

[ChrisRackauckas]

Test fails. Make sure f is not defined in such a way that it has both dispatches. I'd just change its name to something like fscalar or so.