Dear EOSIO developer, ERROR 3050003

[MuesliStreichen]

File: docs/40_smart-contract-guides/70_inline-action-to-external-contract.md

I followed the Manual step by step, but when at Step 6 of the Inline Actions to External Contracts. The terminal always prompts me the following ERROR.
I am very new at programming in general.
Would be blessed if somebody could help.

After I type this command in the console...:
cleos push action addressbook upsert '["alice", "alice", "liddell", 19, "123 drink me way", "wonderland", "amsterdam"]' -p alice@active

This Error appears:
Error 3050003: eosio_assert_message assertion failure
Error Details:
assertion failure with message: datastream attempted to read past the end
pending console output:

I researched a bit on google and think the Error is somehow caused by this section of the code:

void send_summary(name user, std::string message) {
action(
permission_level{get_self(),"active"_n},
get_self(),
"notify"_n,
std::make_tuple(user, name{user}.to_string() + message)
).send();
};