Bugfix for ilist conversion.  The ilist wants to make an 'end' node which has
G == 0

llvm-svn: 11174
diff --git a/llvm/lib/Analysis/DataStructure/DataStructure.cpp b/llvm/lib/Analysis/DataStructure/DataStructure.cpp
index 9311b10..57651d7 100644
--- a/llvm/lib/Analysis/DataStructure/DataStructure.cpp
+++ b/llvm/lib/Analysis/DataStructure/DataStructure.cpp
@@ -74,7 +74,7 @@
   : NumReferrers(0), Size(0), ParentGraph(G), Ty(Type::VoidTy), NodeType(0) {
   // Add the type entry if it is specified...
   if (T) mergeTypeInfo(T, 0);
-  G->addNode(this);
+  if (G) G->addNode(this);
   ++NumNodeAllocated;
 }