Fix issue #1237 so browser doesn't intialize during session reset

lib/capybara/driver/base.rb

@@ -133,4 +133,8 @@ class Capybara::Driver::Base
   def needs_server?
     false
   end
+
+  def browser_initialized?
+    true
+  end
 end

lib/capybara/rack_test/driver.rb

@@ -86,6 +86,10 @@ class Capybara::RackTest::Driver < Capybara::Driver::Base
     @browser = nil
   end
 
+  def browser_initialized?
+    !@browser.nil?
+  end
+
   def get(*args, &block); browser.get(*args, &block); end
   def post(*args, &block); browser.post(*args, &block); end
   def put(*args, &block); browser.put(*args, &block); end

lib/capybara/selenium/driver.rb

@@ -237,6 +237,10 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
     Selenium::WebDriver::Error::NoSuchWindowError
   end
 
+  def browser_initialized?
+    !@browser.nil?
+  end
+
   private
 
   def within_given_window(handle)

lib/capybara/session.rb

@@ -101,7 +101,7 @@ module Capybara
     def reset!
       if @touched
         driver.reset!
-        assert_no_selector :xpath, "/html/body/*"
+        assert_no_selector :xpath, "/html/body/*" if driver.browser_initialized?
         @touched = false
       end
       raise_server_error!