Merge bitcoin#21631: i2p: always check the return value of Sock::Wait()

1c1467f i2p: cancel the Accept() method if waiting on the socket errors (Vasil Dimov)

Pull request description:

  If `Sock::Wait()` fails, then cancel the `Accept()` method.

  Not checking the return value may cause an uninitialized read a few lines below when we read the `occurred` variable.

  [Spotted](bitcoin#21630 (comment)) by MarcoFalke, thanks!

ACKs for top commit:
  laanwj:
    Code review ACK 1c1467f
  practicalswift:
    cr ACK 1c1467f: patch looks correct and agree with laanwj that `[[nodiscard]]` can be taken in a follow-up PR :)

Tree-SHA512: 57fa8a03a4e055999e23121cd9ed1566a585ece0cf68b74223d8c902804cb6890218c9356d60e0560ccacc6c8542a526356c226ebd48e7b299b4572be312d49b

src/i2p.cpp

@@ -147,7 +147,9 @@ bool Session::Accept(Connection& conn)
     try {
         while (!*m_interrupt) {
             Sock::Event occurred;
-            conn.sock->Wait(MAX_WAIT_FOR_IO, Sock::RECV, &occurred);
+            if (!conn.sock->Wait(MAX_WAIT_FOR_IO, Sock::RECV, &occurred)) {
+                throw std::runtime_error("wait on socket failed");
+            }
 
             if ((occurred & Sock::RECV) == 0) {
                 // Timeout, no incoming connections within MAX_WAIT_FOR_IO.