Incorrect return type

[bartoszkubicki]

Incorrect return type is returned if product feed is disabled:

[report]$ cat 1de816e4cac87893a6f1dcecea53fd057d2813245c30f7183e4508fe9e5df609 {"0":"Invalid return type","1":"#1 Magento\\Framework\\App\\Bootstrap->run() called at [pub\/index.php:30]\n","url":"\/reviews\/index\/feed","script_name":"\/index.php","report_id":"1de816e4cac87893a6f1dcecea53fd057d2813245c30f7183e4508fe9e5df609"}