RUBY-3358 Handle nil session is write_worker (#2826)

lib/mongo/retryable/write_worker.rb

@@ -103,8 +103,9 @@ def write_with_retry(write_concern, ending_transaction: false, context:, &block)
       def nro_write_with_retry(write_concern, context:, &block)
         session = context.session
         server = select_server(cluster, ServerSelector.primary, session)
+        options = session&.client&.options || {}
 
-        if session&.client.options[:retry_writes]
+        if options[:retry_writes]
           begin
             server.with_connection(connection_global_id: context.connection_global_id) do |connection|
               yield connection, nil, context

spec/mongo/retryable/write_worker_spec.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Mongo::Retryable::WriteWorker do
+  describe '#nro_write_with_retry' do
+    context 'when session is nil' do
+      let(:retryable) do
+        authorized_client['write_worker_test']
+      end
+
+      let(:write_concern) do
+        Mongo::WriteConcern.get(w: 0)
+      end
+
+      let(:write_worker) do
+        described_class.new(retryable)
+      end
+
+      let(:context) do
+        instance_double(Mongo::Operation::Context).tap do |context|
+          allow(context).to receive(:session).and_return(nil)
+        end
+      end
+
+      before do
+        # We avoid actual execution of the operation to speed up and simplify
+        # the spec.
+        allow(write_worker).to receive(:legacy_write_with_retry).and_return(nil)
+      end
+
+      it 'does not raise' do
+        expect do
+          write_worker.nro_write_with_retry(write_concern, context: context)
+        end.not_to raise_error
+      end
+    end
+  end
+end