[ns] Classfier::no-slot{} default handler (tcl/lib/ns-lib.tcl)

[Xie Sheng]

hi,  s9256014 at cs.nchu.edu.tw 
check if you have attached agent such as Null and TCPSink correctly.
and you must also pay attention to your topology if you use
hierachical address. a node cannot directly connect more than one
node belonging to a different domain(the first fragment in the address),
or else the routes would have some trouble. for example, if you connect
nodes of 0.0.0, 0.1.0 and 0.2.0 to 1.0.0, the packets may not be  
routed from domain 1 to the right cluster in domain 0.