Fix the query extension to handle blocks that end in nil.

lib/sequel/extensions/query.rb

@@ -29,7 +29,9 @@ class Dataset
     #
     #  dataset = DB[:items].select(:x, :y, :z).filter{(x > 1) & (y > 2)}.reverse(:z)
     def query(&block)
-      Query.new(self).instance_eval(&block).dataset
+      query = Query.new(self)
+      query.instance_eval(&block)
+      query.dataset
     end
 
     # Proxy object used by Dataset#query.

spec/extensions/query_spec.rb

@@ -77,6 +77,15 @@
     q.class.should == @d.class
     q.sql.should == "SELECT * FROM xyz ORDER BY stamp"
   end
+
+  specify "should support blocks that end in nil" do
+    condition = false
+    q = @d.query do
+      from :xyz
+      order_by :stamp if condition
+    end
+    q.sql.should == "SELECT * FROM xyz"
+  end
 
   specify "should raise on non-chainable method calls" do
     proc {@d.query {row_proc}}.should raise_error(Sequel::Error)