8180617: Null pointer dereference in InitializeNode::complete_stores

Summary: Fixed a missing null check on the return value of InitializeNode::allocation() found by Parfait.
Reviewed-by: zmajo

src/share/vm/opto/memnode.cpp

@@ -4035,9 +4035,10 @@ Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
     // if it is the last unused 4 bytes of an instance, forget about it
     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
     if (zeroes_done + BytesPerLong >= size_limit) {
-      assert(allocation() != NULL, "");
-      if (allocation()->Opcode() == Op_Allocate) {
-        Node* klass_node = allocation()->in(AllocateNode::KlassNode);
+      AllocateNode* alloc = allocation();
+      assert(alloc != NULL, "must be present");
+      if (alloc != NULL && alloc->Opcode() == Op_Allocate) {
+        Node* klass_node = alloc->in(AllocateNode::KlassNode);
         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
         if (zeroes_done == k->layout_helper())
           zeroes_done = size_limit;