Return empty string rather than nil for accessible autocomplete

app/helpers/filters_helper.rb

@@ -20,6 +20,6 @@ module FiltersHelper
   def selected_option(filter)
     return false unless session[:case_logs_filters]
 
-    JSON.parse(session[:case_logs_filters])[filter]
+    JSON.parse(session[:case_logs_filters])[filter] || ""
   end
 end

spec/helpers/filters_helper_spec.rb

@@ -69,4 +69,16 @@ RSpec.describe FiltersHelper do
       end
     end
   end
+
+  describe "#selected_option" do
+    before do
+      session[:case_logs_filters] = {}.to_json
+    end
+
+    context "when nothing has been selected" do
+      it "returns an empty string" do
+        expect(selected_option("organisation")).to eq("")
+      end
+    end
+  end
 end