Internal error when trying to find string definition of `Base.get_preferences`

[KristofferC]

julia> m = which(Base.get_preferences, Tuple{Base.UUID})
get_preferences(uuid::Union{Nothing, Base.UUID}) in Base at loading.jl:2006

julia> CodeTracking.definition(String, m)
ERROR: MethodError: no method matching +(::Nothing, ::Int64)
Closest candidates are:
  +(::Any, ::Any, ::Any, ::Any...) at operators.jl:591
  +(::T, ::T) where T<:Union{Int128, Int16, Int32, Int64, Int8, UInt128, UInt16, UInt32, UInt64, UInt8} at int.jl:87
  +(::T, ::Integer) where T<:AbstractChar at char.jl:237
  ...
Stacktrace:
 [1] definition(#unused#::Type{String}, method::Method)
   @ CodeTracking ~/.julia/packages/CodeTracking/rwfOQ/src/CodeTracking.jl:230
 [2] top-level scope
   @ REPL[4]:1