Demo can't parse json responses as they lead with a warning in html

[Robsteranium]

I was trying to use the console demo. When I try to invoke GET /hydra/api-demo/issues/ nothing happens and I see this error in the console:

Uncaught SyntaxError: JSON.parse: unexpected character at line 2 column 1 of the JSON data

Inspecting the response you see it leads with what appears to be a warning from PHP:

<br />
<b>Warning</b>:  "continue" targeting switch is equivalent to "break". Did you mean to use "continue 2"? in <b>/nfs/c03/h01/mnt/51450/domains/markus-lanthaler.com/hydra-demo/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php</b> on line <b>2549</b><br />
{
    "@context": "/hydra/api-demo/contexts/Collection.jsonld",
    ...