hst:facetnavigationlink removes facet values with similar names

When you have facet values with similar names such as 'Energy' and 'Energy conservation', both facets are removed when you want to remove 'Energy' using the hst:facetnavigationlink.

Reproduction path:

• go to https://cms.demo.onehippo.com/ and log in as admin
• go to /content/documents/hippogogreen/news/2012/10 and select an existing news document
• Add the following values to the 'Categories' field: 'Energy' and 'Energy conservation'
• Save & close the document and then publish it
• go to http://www.demo.onehippo.com/news/faceted/News+Category/Energy/News+Category/Energy+conservation and click on the 'Energy' link with the cross next to it to remove the facet value.
• You are sent to a 404 page due to a malformed URL