fix a few tests

Author: ChrisRackauckas

src/systems/diffeqs/abstractodesystem.jl

@@ -864,7 +864,7 @@ function process_DEProblem(constructor, sys::AbstractODESystem, u0map, parammap;
 
     # TODO: Pass already computed information to varmap_to_vars call
     # in process_u0? That would just be a small optimization
-    varmap = isempty(u0map) || eltype(u0map) <: Number ? defaults(sys) :
+    varmap = (u0map !== nothing && isempty(u0map)) || eltype(u0map) <: Number ? defaults(sys) :
              merge(defaults(sys), todict(u0map))
     varlist = collect(map(unwrap, dvs))
     missingvars = setdiff(varlist, collect(keys(varmap)))

test/initializationsystem.jl

@@ -358,7 +358,7 @@ sol = solve(prob, Tsit5())
 
 ## Late binding initialization_eqs
 
-function System(; name)
+function System2(; name)
     vars = @variables begin
         dx(t), [guess = 0]
         ddx(t), [guess = 0]
@@ -371,7 +371,7 @@ function System(; name)
     return ODESystem(eqs, t, vars, []; name, initialization_eqs)
 end
 
-@mtkbuild sys = System()
+@mtkbuild sys = System2()
 prob = ODEProblem(sys, [], (0, 1), guesses = [sys.dx => 1])
 sol = solve(prob, Tsit5())
 @test SciMLBase.successful_retcode(sol)