Fix unreachable code warning in tests

include/boost/beast/core/impl/buffers_cat.hpp

@@ -61,13 +61,11 @@ public:
 #define BOOST_BEAST_LOGIC_ERROR(s) \
     { \
         BOOST_THROW_EXCEPTION(std::logic_error((s))); \
-        BOOST_BEAST_UNREACHABLE(); \
     }
 
 #define BOOST_BEAST_LOGIC_ERROR_RETURN(s, v) \
     { \
         BOOST_THROW_EXCEPTION(std::logic_error((s))); \
-        return v; \
     }
 
 #else
@@ -94,13 +92,6 @@ struct buffers_cat_view_iterator_base
     {
         char unused = 0; // make g++8 happy
 
-        net::mutable_buffer
-        operator*() const
-        {
-            BOOST_BEAST_LOGIC_ERROR_RETURN(
-                    "Dereferencing a one-past-the-end iterator", {});
-        }
-
         operator bool() const noexcept
         {
             return true;
@@ -189,6 +180,13 @@ private:
                 "Dereferencing a default-constructed iterator", {});
         }
 
+        reference
+        operator()(mp11::mp_size_t<sizeof...(Bn)+1>)
+        {
+            BOOST_BEAST_LOGIC_ERROR_RETURN(
+                "Dereferencing a one-past-the-end iterator", {});
+        }
+
         template<class I>
         reference operator()(I)
         {