Codechange: ensure OnConnect() always gets called with a valid socket (#9729)

This should already be the case, but now assert()s will tell us
if this isn't.

src/network/network_turn.cpp

@@ -41,7 +41,7 @@ public:
 	{
 		this->handler->connecter = nullptr;
 
-		handler->sock = s;
+		this->handler->sock = s;
 	}
 };