Look at vertices with minimum degree 0 first instead of starting with those with minimum degree 1 (fix courtesy of Roman Dementiev)

[SVN r33414]

libs/graph

@@ -1 +1 @@
-Subproject commit dea8296e5bfaeb1099fb6e4a6dc6daa696210b7b
+Subproject commit 5597592ff5cc1a5d0c35ecaf21ea8b14d989fcd1