check for empty inputs; closes #448

src/series.jl

@@ -125,22 +125,20 @@ immutable SliceIt end
     mx = length(xs)
     my = length(ys)
     mz = length(zs)
-    # ret = Any[]
+    if mx > 0 && my > 0 && mz > 0
         for i in 1:max(mx, my, mz)
             # add a new series
             di = copy(d)
             xi, yi, zi = xs[mod1(i,mx)], ys[mod1(i,my)], zs[mod1(i,mz)]
-        # @show i, typeof((xi, yi, zi))
             di[:x], di[:y], di[:z] = compute_xyz(xi, yi, zi)
-        # @show i, typeof((di[:x], di[:y], di[:z]))
 
             # handle fillrange
             fr = fillranges[mod1(i,mf)]
             di[:fillrange] = isa(fr, Function) ? map(fr, di[:x]) : fr
 
-        # @show i, di[:x], di[:y], di[:z]
             push!(series_list, RecipeData(di, ()))
         end
+    end
     nothing  # don't add a series for the main block
 end