fix empty reduce issue

Author: wupeifan

src/build_function.jl

@@ -114,7 +114,7 @@ function _build_function(target::JuliaTarget, rhss, args...;
 	elseif eltype(rhss) <: SparseMatrixCSC # Array of sparse matrices
 		ip_sys_exprs = reduce(vcat,[vec([:($X[$i].nzval[$j] = $(conv(rhs))) for (j, rhs) ∈ enumerate(rhsel)]) for (i,rhsel) ∈ enumerate(rhss)])
     elseif eltype(rhss) <: AbstractArray # Array of arrays
-		ip_sys_exprs = reduce(vcat,[vec([:($X[$i][$j] = $(conv(rhs))) for (j, rhs) ∈ enumerate(rhsel)]) for (i,rhsel) ∈ enumerate(rhss)])
+		ip_sys_exprs = reduce(vcat,[vec([:($X[$i][$j] = $(conv(rhs))) for (j, rhs) ∈ enumerate(rhsel)]) for (i,rhsel) ∈ enumerate(rhss)], init = Expr[])
     elseif rhss isa SparseMatrixCSC
         ip_sys_exprs = [:($X.nzval[$i] = $(conv(rhs))) for (i, rhs) ∈ enumerate(rhss.nzval)]
     else