LibHTML: Make the HTML parser handle <div attr> and <div attr="">

We were not producing the correct DOM attribute in either of those
cases. "<div attr>" would produce no attribute, and the other would
produce an attribute with null value (instead of an empty value.)

Libraries/LibHTML/Parser/HTMLParser.cpp

@@ -118,7 +118,15 @@ static bool parse_html_document(const StringView& html, Document& document, Pare
     };
 
     auto commit_attribute = [&] {
-        attributes.append({ String::copy(attribute_name_buffer), String::copy(attribute_value_buffer) });
+        if (!attribute_name_buffer.is_empty()) {
+            auto name = String::copy(attribute_name_buffer);
+            String value;
+            if (attribute_value_buffer.is_empty())
+                value = String::empty();
+            else
+                value = String::copy(attribute_value_buffer);
+            attributes.empend(name, value);
+        }
     };
 
     for (int i = 0; i < html.length(); ++i) {
@@ -243,6 +251,7 @@ static bool parse_html_document(const StringView& html, Document& document, Pare
             }
 
             if (ch == '>') {
+                commit_attribute();
                 commit_tag();
                 move_to_state(State::Free);
                 break;