Fix -Wunused-lambda-capture warning with clang-5

Change-Id: Ib9f3bafbf3ff6790caf19f25f2c820d8540d4000
diff --git a/src/handles/read-handle.cpp b/src/handles/read-handle.cpp
index 1f13bf3..897fab1 100644
--- a/src/handles/read-handle.cpp
+++ b/src/handles/read-handle.cpp
@@ -48,7 +48,6 @@
 void
 ReadHandle::onInterest(const Name& prefix, const Interest& interest)
 {
-
   shared_ptr<ndn::Data> data = getStorageHandle().readData(interest);
   if (data != nullptr) {
       getFace().put(*data);
@@ -106,8 +105,7 @@
         // Implicit conversion to Name of filter
         onInterest(filter, interest);
       },
-      [this] (const Name& prefix) {
-      },
+      [] (const Name&) {},
       [this] (const Name& prefix, const std::string& reason) {
         onRegisterFailed(prefix, reason);
       });