Strip_tags never ending attribute should not raise a TypeError [#4870 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>

actionpack/lib/action_controller/vendor/html-scanner/html/node.rb

@@ -177,6 +177,7 @@ module HTML #:nodoc:
                     case text
                       when "\\" then
                         value << text
+                        break if scanner.eos?
                         value << scanner.getch
                       when delim
                         break

actionpack/lib/action_controller/vendor/html-scanner/html/tokenizer.rb

@@ -96,6 +96,7 @@ module HTML #:nodoc:
           while match = @scanner.scan_until(/[\\#{delim}]/)
             text << match
             break if @scanner.matched == delim
+            break if @scanner.eos?
             text << @scanner.getch # skip the escaped character
           end
         end

actionpack/test/template/html-scanner/sanitizer_test.rb

@@ -257,6 +257,10 @@ class SanitizerTest < ActionController::TestCase
      assert_sanitized %{<a href=\"http://www.domain.com?var1=1&amp;var2=2\">my link</a>}
   end
 
+  def test_should_sanitize_neverending_attribute
+    assert_sanitized "<span class=\"\\", "<span class=\"\\\">"
+  end
+
 protected
   def assert_sanitized(input, expected = nil)
     @sanitizer ||= HTML::WhiteListSanitizer.new