undefined link when using language switcher

hello ..

installed polylang in free version and i have 2 languages ( English & arabic ) with english is the default … and i translated just the homepage to test plugin

this is english homepage link : http://investorsmgz.com/
this is arabic homepage link : http://investorsmgz.com/ar/

now when i try the language switcher to redirect to the home page in other langauge it gives me another link that is : http://investorsmgz.com/undefined

Can you help me of that please ..?

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