fix XML::Reader working with non-existent attributes

nokogiri now bundles a newer libxml, so doesn't have to
worry about old bad behavior, and the workaround was broken

ext/nokogiri/xml_reader.c

@@ -219,19 +219,6 @@ static VALUE reader_attribute(VALUE self, VALUE name)
   name = StringValue(name) ;
 
   value = xmlTextReaderGetAttribute(reader, (xmlChar*)StringValueCStr(name));
-  if(value == NULL) {
-    /* this section is an attempt to workaround older versions of libxml that
-       don't handle namespaces properly in all attribute-and-friends functions */
-    xmlChar *prefix = NULL ;
-    xmlChar *localname = xmlSplitQName2((xmlChar*)StringValueCStr(name), &prefix);
-    if (localname != NULL) {
-      value = xmlTextReaderLookupNamespace(reader, localname);
-      xmlFree(localname) ;
-    } else {
-      value = xmlTextReaderLookupNamespace(reader, prefix);
-    }
-    xmlFree(prefix);
-  }
   if(value == NULL) return Qnil;
 
   rb_value = NOKOGIRI_STR_NEW2(value);

test/xml/test_reader.rb

@@ -576,6 +576,14 @@ def test_correct_inner_xml_inclusion
         assert(has_child2[1])
         assert(!has_child2[0])
       end
+
+      def test_nonexistent_attribute
+        require 'nokogiri'
+        reader = Nokogiri::XML::Reader("<root xmlns='bob'><el attr='fred' /></root>")
+        reader.read
+        reader.read
+        assert_equal reader.attribute('other'), nil
+      end
     end
   end
 end