CBL-7013: Native crash when using LiteCore 3.3.0-80 (#2299)

* CBL-7013: Native crash when using LiteCore 3.3.0-80

I used LiteCore 3.3.0-80 to reproduce the native crash when the following tests are reinstated,
- ReplicatorPendingDocIdTest
- ReplicatorLocal2LocalTest

The issue is specific to LoopbackWebSocket. We need to guard against the case when Replicator::_onConnect comes after it is stopped.

Author: jianminzhao

Replicator/Replicator.cc

@@ -607,6 +607,14 @@ namespace litecore::repl {
     }
 
     void Replicator::_onConnect() {
+        // onConnect may come after the replicator is asked to stop. This situation is
+        // guarded against in WebSocketImpl::onConnect. However, LoopbackWebSocket does
+        // not go throuth WebSocketImpl. We catch the case here.
+        if ( _connectionState != Connection::kConnecting ) {
+            logInfo("Replicator not in connecting state (connectionState=%d); ignoring onConnect.", _connectionState);
+            return;
+        }
+
         logInfo("Connected!");
 
         if ( auto socket = connection().webSocket(); socket->role() == websocket::Role::Client ) {