fix of TypedID bug in CCNxContentObjectTail

diff --git a/model/ccnx-content-object-header.cc b/model/ccnx-content-object-header.cc
index 46a1554..8da3b84 100644
--- a/model/ccnx-content-object-header.cc
+++ b/model/ccnx-content-object-header.cc
@@ -97,7 +97,7 @@
 TypeId
 CcnxContentObjectTail::GetTypeId (void)
 {
-  static TypeId tid = TypeId ("ns3::CcnxContentObjectHeader")
+  static TypeId tid = TypeId ("ns3::CcnxContentObjectTail")
     .SetParent<Header> ()
     .AddConstructor<CcnxContentObjectHeader> ()
     ;