Bug fixes in content router for enabling Advanced option

This fixes two bugs that exist when enabling Advanced SEF in content router and is complimentary to #4246

How to test:
Faulty assumption that an alias will be article
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Create a new category
Create a new article in that category
Create a menu pointing in that article
navigate to that article
click on the category link
get a nice 404 error 

The duplicate alias name on different languages
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Create a multilingual env
Create a menu in english named faulty
Create in the second language a menu test
Create another menu named faulty with parent the menu test
try to access faulty in english and in the other language 
get a nice 404 error

Apply the patch and try to access the broken links!