Merge pull request #390 from jgray-19/mtable_additions

Add mtable fix for `read` to work

Author: ldeniau

src/madl_mtable.mad

@@ -988,7 +988,7 @@ local function add_row (tbl, val)
                                     "invalid argument #3 (nil reference value)")
   local nr = data.nr+1
   if nr > data.rmax then expand(data, tbl, 1) end
-  local nn = val[1] ~= nil and #val or data.nc-data.ng
+  local nn = val.n or val[1] ~= nil and #val or data.nc-data.ng
   for ci=1,nn do
     local v = val[ci]
     if is_nil(v) then v = val[data.cidx[ci]] end