FILTER in FILTER EXISTS not properly handled

[vcharpenay]

Example pattern:

?o a owl:Ontology ;
   vann:preferredNamespaceUri ?ns .
filter exists {
    ?i a ?c .
    ?c rdfs:subClassOf schema:Enumeration .
    filter (strstarts(str(?i), str(?ns)))
}

example doc: td.ttl.

Expected results but none found.

[vcharpenay]

Same in optional (same bug?).

?c a skos:Concept
optional {
  ?c skos:editiorialNote ?note .
  filter (contains(?note, "notaword"))
}

won't return any result although some skos:Concept are defined.

[vcharpenay]

bug in optional was due to an error in makeSafe. Now fixed (e600344) but query evaluation is significantly slower (duplicate evaluations).