Merge pull request #20547 from azat/fix-sigsegv-on-unknown-packet

Fix SIGSEGV on Unknown packet for Distributed queries

src/Client/Connection.cpp

@@ -756,7 +756,11 @@ std::optional<UInt64> Connection::checkPacket(size_t timeout_microseconds)
 Packet Connection::receivePacket(std::function<void(Poco::Net::Socket &)> async_callback)
 {
     in->setAsyncCallback(std::move(async_callback));
-    SCOPE_EXIT(in->setAsyncCallback({}));
+    SCOPE_EXIT({
+        /// disconnect() will reset "in".
+        if (in)
+            in->setAsyncCallback({});
+    });
 
     try
     {