Comment 2 for bug 944198

StacktraceTop:
 foreach_nodetree (main=0x0, calldata=0xa5181d0, func=0x84286b0 <ntree_verify_nodes_cb>) at /build/buildd/blender-2.61/source/blender/nodes/shader/node_shader_tree.c:68
 ntreeVerifyNodes (main=0x0, id=0xa5181d0) at /build/buildd/blender-2.61/source/blender/blenkernel/intern/node.c:1476
 ntreeUpdateTree (ntree=0xa5181d0) at /build/buildd/blender-2.61/source/blender/blenkernel/intern/node.c:1531
 lib_nodetree_do_versions_update_cb (UNUSED_data=0x0, UNUSED_id=0xa5174c0, ntree=0xa5181d0) at /build/buildd/blender-2.61/source/blender/blenloader/intern/readfile.c:2244
 foreach_nodetree (main=0xa15e970, calldata=0x0, func=0x84aecf0 <lib_nodetree_do_versions_update_cb>) at /build/buildd/blender-2.61/source/blender/nodes/shader/node_shader_tree.c:70