rib: Update to properly handle optional ExpirationPeriod in RibRegister command

Change-Id: I9f18988f295a993e53dc03547f2f20967431dc10
Refs: #1772
diff --git a/rib/rib-manager.cpp b/rib/rib-manager.cpp
index c8d6111..d9c88e2 100644
--- a/rib/rib-manager.cpp
+++ b/rib/rib-manager.cpp
@@ -227,7 +227,8 @@
   faceEntry.cost = parameters.getCost();
   faceEntry.flags = parameters.getFlags();
 
-  if (parameters.getExpirationPeriod() != time::milliseconds::max())
+  if (parameters.hasExpirationPeriod() &&
+      parameters.getExpirationPeriod() != time::milliseconds::max())
     {
       faceEntry.expires = time::steady_clock::now() + parameters.getExpirationPeriod();