face-management-protocol: Fixing small bug with ForwardingEntry

The daemon always expects Prefix entry, even though it is defined
optional in the protocol.

Change-Id: I4ade13897af8e47944be2384a2fc116959e50d15
diff --git a/include/ndn-cpp/forwarding-entry.hpp b/include/ndn-cpp/forwarding-entry.hpp
index e9a3f47..182dc38 100644
--- a/include/ndn-cpp/forwarding-entry.hpp
+++ b/include/ndn-cpp/forwarding-entry.hpp
@@ -108,11 +108,8 @@
     }
 
   // Name
-  if (!prefix_.empty())
-    {
-      wire_.push_back
-        (prefix_.wireEncode());
-    }
+  wire_.push_back
+    (prefix_.wireEncode());
 
   // FaceID
   if (faceId_ >= 0)
@@ -203,10 +200,7 @@
     }
 
   // Name
-  if (!entry.getPrefix().empty())
-    {
-      os << "Prefix:" << entry.getPrefix() << ", ";
-    }
+  os << "Prefix:" << entry.getPrefix() << ", ";
 
   // FaceID
   if (entry.getFaceId() >= 0)