Improve checkpointing of ethernet packets a bit.

dev/etherpkt.cc:
    Don't try to suck in the packet if the length is zero.

--HG--
extra : convert_revision : 7212f3b677777fbce301f0613b9f513bb9fe057e

dev/etherpkt.cc

@@ -46,5 +46,6 @@ PacketData::unserialize(const string &base, Checkpoint *cp,
                         const string &section)
 {
     paramIn(cp, section, base + ".length", length);
-    arrayParamIn(cp, section, base + ".data", data, length);
+    if (length)
+        arrayParamIn(cp, section, base + ".data", data, length);
 }