Update src/extension_algs.jl

Author: ChrisRackauckas

src/extension_algs.jl

@@ -95,8 +95,7 @@ Additional optimization for complex matrices is in the works.
 """
 struct RFLUFactorization{P, T} <: AbstractDenseFactorization
     function RFLUFactorization(::Val{P}, ::Val{T}; throwerror = true) where {P, T}
-        ext = Base.get_extension(@__MODULE__, :LinearSolveRecursiveFactorizationExt)
-        if ext === nothing
+        if userecursivefactorization(nothing)
             throwerror &&
                 error("RFLUFactorization requires that RecursiveFactorization.jl is loaded, i.e. `using RecursiveFactorization`")
         end