The API returns links that does not exist when setting ``depth`` to 1

[WoodenMaiden]

When setting depth to 1 self loops and non existing inks start to appear:

Using the test dataset we have these results:

Request payload:

{"nodes":["http://people.local/yann","http://games.local/leagueoflegends/champions/irelia"]}

Here we can see that no direct link to http://games.local/leagueoflegends/champions/irelia, nor self loop to http://people.local/yann exists

cat ./test/test_dataset.ttl | grep 'http://people.local/yann'
<http://people.local/yann> ppl:name "Yann" .
<http://people.local/yann> rdfs:label "Yann" .
<http://people.local/yann> ppl:username "WoodenMaiden" .
<http://people.local/someUser> ppl:hasfriend <http://people.local/yann> .
<http://people.local/yann> ppl:hasfriend <http://people.local/someUser> .
<http://people.local/yann> rdf:type <http://people.local/types/player> .
<http://people.local/yann> ppl:plays <http://games.local/leagueoflegends> .
<http://people.local/yann> ppl:mains <http://games.local/leagueoflegends/champions/ryze> .
<http://people.local/yann> ppl:mains <http://games.local/leagueoflegends/champions/yorick> .
<http://people.local/yann> ppl:plays <http://games.local/warframe> .
<http://people.local/yann> ppl:uses <http://games.local/warframe/weapons/igniswrath> .
<http://people.local/yann> ppl:uses <http://games.local/warframe/weapons/brakkkuva> .
<http://people.local/yann> ppl:uses <http://games.local/warframe/weapons/mire> .
<http://people.local/yann> ppl:mains <http://games.local/warframe/frame/garuda> .