Logical OR with sum does not work when using two product attributes.

Steps:

1. Create Product Type with some attributes.
2. Use URL alias name pattern like <description|(<attribute:mouse_type> <attribute:mouse_weight>)>.
3. Create Product. Leave description empty. Provide both attributes with values.
4. Publish.
5. Check URL.

Actual result: URL contains only the value from second attribute.
Expected result: URL contains values from both attributes.