Fix crashes when auth failed (#2736)

src/emqx_protocol.erl

@@ -74,7 +74,7 @@ info(#protocol{client     = Client,
                will_msg   = WillMsg,
                topic_aliases = Aliases}) ->
     #{client => Client,
-      session => emqx_session:info(Session),
+      session => session_info(Session),
       proto_name => ProtoName,
       proto_ver => ProtoVer,
       keepalive => Keepalive,
@@ -606,7 +606,7 @@ auth_connect(#mqtt_packet_connect{client_id = ClientId,
         {ok, AuthResult} ->
             {ok, PState#protocol{client = maps:merge(Client, AuthResult)}};
         {error, Reason} ->
-            ?LOG(warning, "Client ~s (Username: '~s') login failed for ~p",
+            ?LOG(warning, "Client ~s (Username: '~s') login failed for ~0p",
                  [ClientId, Username, Reason]),
             {error, emqx_reason_codes:connack_error(Reason)}
     end.
@@ -916,3 +916,8 @@ sp(false) -> 0.
 
 flag(true)  -> 1;
 flag(false) -> 0.
+
+session_info(undefined) ->
+    undefined;
+session_info(Session) ->
+    emqx_session:info(Session).