Call store_location_for once.

app/controllers/sessions_controller.rb

 class SessionsController < Devise::SessionsController
 
   def new
-    if request.referer.present?
+    redirect_url = if request.referer.present?
                      referer_uri = URI(request.referer)
                      if referer_uri.host == Gitlab.config.gitlab.host
-        store_location_for(:redirect, referer_uri.path)
+                       referer_uri.path
                      else
-        store_location_for(:redirect, request.fullpath)
+                       request.fullpath
                      end
                    else
-      store_location_for(:redirect, request.fullpath)
+                     request.fullpath
                    end
 
+    store_location_for(:redirect, redirect_url)
+
     super
   end