Strip markup from selected facet values in the html title.

- E.g., span/data-attributes rendered for selected range facet values by blacklight_range_limit
- Fixes projectblacklight/blacklight_range_limit#189

app/helpers/blacklight/catalog_helper_behavior.rb

@@ -136,7 +136,7 @@ def render_search_to_page_title_filter(facet, values)
                    else
                      t('blacklight.search.page_title.many_constraint_values', values: values.size)
                    end
-    t('blacklight.search.page_title.constraint', label: filter_label, value: filter_value)
+    t('blacklight.search.page_title.constraint', label: filter_label, value: strip_tags(filter_value))
   end
 
   # Render an html <title> appropriate string for a set of search parameters

spec/helpers/catalog_helper_spec.rb

@@ -261,6 +261,10 @@ def mock_response args
     it "renders a facet with more than two values" do
       expect(helper.render_search_to_page_title_filter('foo', %w[bar baz foobar])).to eq "Foo: 3 selected"
     end
+
+    it "strips tags from values" do
+      expect(helper.render_search_to_page_title_filter('Year', ['<span class="from" data-blrl-begin="1990">1990</span> to <span class="to" data-blrl-end="1999">1999</span>'])).to eq "Year: 1990 to 1999"
+    end
   end
 
   describe "#render_search_to_page_title" do