PrettyForm generates some garbage at end

[ggrothendieck]

This works except that it also generates some garbage (unprocessed XML) at the end.

> library(Ryacas)
> d <- Sym("d")
> S <- (281*d^6)/128+((-65)*d^5)/32+(29*d^4)/16+((-3)*d^3)/2+d^2
> PrettyForm(S)

       6         5         4        3     
281 * d    65 * d    29 * d    3 * d     2
-------- - ------- + ------- - ------ + d 
  128        32        16        2        

<OMOBJ>
  <OMS cd="logic1" name="true"/>
</OMOBJ>