Self closing tags returning "" instead of nil

It was discovered that self closing tags return "" now instead of nil.

Discussed the possible fixes on:
#443

Author: netikular

lib/onelogin/ruby-saml/utils.rb

@@ -286,7 +286,7 @@ def self.original_uri_match?(destination_url, settings_url)
       # that there all children other than text nodes can be ignored (e.g. comments). If nil is
       # passed, nil will be returned.
       def self.element_text(element)
-        element.texts.join if element
+        element.texts.join if element && !element.texts.empty?
       end
     end
   end

test/response_test.rb

@@ -1129,12 +1129,12 @@ class RubySamlTest < Minitest::Test
 
         it "return multiple values including nil and empty string" do
           response = OneLogin::RubySaml::Response.new(fixture(:response_with_multiple_attribute_values))
-          assert_equal ["", "valuePresent", nil, nil], response.attributes.multi(:attribute_with_nils_and_empty_strings)
+          assert_equal [nil, "valuePresent", nil, nil], response.attributes.multi(:attribute_with_nils_and_empty_strings)
         end
 
         it "return multiple values from [] when not in compatibility mode off" do
           OneLogin::RubySaml::Attributes.single_value_compatibility = false
-          assert_equal ["", "valuePresent", nil, nil], response_multiple_attr_values.attributes[:attribute_with_nils_and_empty_strings]
+          assert_equal [nil, "valuePresent", nil, nil], response_multiple_attr_values.attributes[:attribute_with_nils_and_empty_strings]
           OneLogin::RubySaml::Attributes.single_value_compatibility = true
         end