Unknown SEO URLs not returning 404 fixes

https://github.com/opencart/opencart/commit/4357ab491ce55247a34e09030054f732eb7f226d

https://github.com/opencart/opencart/commit/9f7e4c983c82585422ba7e91e54b3c3aa7b0cf08

https://github.com/opencart/opencart/commit/0f529b9792c21e16dffbe90b549dcee5cc98d9f5