Fix literal_getproperty for LinearSolution

Author: avik-pal

ext/SciMLBaseZygoteExt.jl

@@ -167,6 +167,15 @@ end
     sol.u, solu_adjoint
 end
 
+@adjoint function literal_getproperty(sol::SciMLBase.LinearSolution, ::Val{:u})
+    function solu_adjoint(Δ)
+        zerou = zero(sol.u)
+        _Δ = @. ifelse(Δ === nothing, zerou, Δ)
+        (SciMLBase.build_linear_solution(sol.cache.alg, _Δ, sol.resid, sol.cache),)
+    end
+    sol.u, solu_adjoint
+end
+
 @adjoint function literal_getproperty(sol::SciMLBase.OptimizationSolution,
         ::Val{:u})
     function solu_adjoint(Δ)