null_u0_callbacks test stalls on Julia pre-release versions

[ChrisRackauckas-Claude]

Description

The null_u0_callbacks_test.jl test stalls/hangs when running on Julia pre-release versions. The test runs indefinitely without completing or timing out.

Test File

test/interface/null_u0_callbacks_test.jl

Behavior

• On Julia LTS (1.10): Fails with MethodError: no method matching oneunit(::Type{Any})
• On Julia stable (1.11, 1.x): Works correctly
• On Julia pre-release: Stalls/hangs indefinitely

Current Workaround

The test is skipped on both Julia LTS and pre-release versions in PR #2971:

if VERSION >= v"1.11" && isempty(VERSION.prerelease)
    @time @safetestset "Null u0 Callbacks Tests" include("interface/null_u0_callbacks_test.jl")
end

Investigation Needed

• Determine what causes the test to stall on pre-release
• May be related to changes in Julia's type system or callback handling in pre-release
• Could be an infinite loop triggered by specific edge cases with u0 = nothing

Related Issues

• The test was added to support MTK issue ModelingToolkit.jl#4078
• This test specifically exercises solving ODEProblems with null u0 and callbacks

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