fix rangespace for PiecewiseSpace

Author: jishnub

src/Spaces/ProductSpaceOperators.jl

@@ -228,7 +228,7 @@ for (Op,OpWrap) in ((:Derivative,:DerivativeWrapper),(:Integral,:IntegralWrapper
             assert_integer(k)
             t = map(s->$Op(s,k),components(S))
             allbanded = all(isbanded, t)
-            ds, rs = S, SumSpace(map(rangespace, t))
+            ds, rs = S, PiecewiseSpace(map(rangespace, t))
             D = Diagonal(convert_vector_or_svector(t))
             bw = interlace_bandwidths(D, ds, rs, allbanded)
             O = InterlaceOperator(D, ds, rs, bw)