Don't try to read empty responses (fixes issues on jruby)

lib/capybara/driver/webkit/browser.rb

@@ -143,9 +143,13 @@ class Capybara::Driver::Webkit
 
     def read_response
       response_length = @connection.gets.to_i
-      response = @connection.read(response_length)
-      response.force_encoding("UTF-8") if response.respond_to?(:force_encoding)
-      response
+      if response_length > 0
+        response = @connection.read(response_length)
+        response.force_encoding("UTF-8") if response.respond_to?(:force_encoding)
+        response
+      else
+        ""
+      end
     end
 
     def default_proxy_options

spec/browser_spec.rb

@@ -158,4 +158,16 @@ describe Capybara::Driver::Webkit::Browser do
       @proxy_requests.size.should == 0
     end
   end
+
+  it "doesn't try to read an empty response" do
+    connection = stub("connection")
+    connection.stub(:puts)
+    connection.stub(:print)
+    connection.stub(:gets).and_return("ok\n", "0\n")
+    connection.stub(:read).and_raise(StandardError.new("tried to read empty response"))
+
+    browser = Capybara::Driver::Webkit::Browser.new(connection)
+
+    expect { browser.visit("/") }.not_to raise_error(/empty response/)
+  end
 end