llvm-ps-dump: fix background color of errorneous nodes
llvm-ps-dump: fix background color of errorneous nodes

We want the nodes that have no points-to (and should have)
to be coloured red. This was not working because there were
no style=filled attribute in the node.

Signed-off-by: Marek Chalupa <b10e113ac36de0a194e1c1a71340ff6b6b99ebfb@mail.muni.cz>

mchalupa/dg,mchalupa/dg,mchalupa/dg,mchalupa/dg