Use safe navigation operator to conditionally check if a user exists

This is needed because we're now allowing a user to delete any of their active sessions. This means that is a user is logged into multiple devices, their session could be deleted while they're still using the application mid-request.

Author: stevepolitodesign

app/controllers/concerns/authentication.rb

@@ -46,7 +46,7 @@ def store_location
 
   def current_user
     Current.user = if session[:current_active_session_id].present?
-      ActiveSession.find_by(id: session[:current_active_session_id]).user
+      ActiveSession.find_by(id: session[:current_active_session_id])&.user
     elsif cookies.permanent.encrypted[:remember_token].present?
       User.find_by(remember_token: cookies.permanent.encrypted[:remember_token])
     end

test/test_helper.rb

@@ -11,7 +11,7 @@ class ActiveSupport::TestCase
 
   # Add more helper methods to be used by all tests here...
   def current_user
-    session[:current_active_session_id] && ActiveSession.find_by(id: session[:current_active_session_id]).user
+    session[:current_active_session_id] && ActiveSession.find_by(id: session[:current_active_session_id])&.user
   end
 
   def login(user, remember_user: nil)