QTextDocument asserts on specific usage of CSS border-width

 442│ void ValueExtractor::lengthValues(const Declaration &decl, int *m)
 443│ {
 444│     if (decl.d->parsed.isValid()) {
 445│         QList<QVariant> v = decl.d->parsed.toList();
 446│         for (int i = 0; i < 4; i++)
 447├───────────> m[i] = lengthValueFromData(qvariant_cast<LengthData>(v.at(i)), f);
 448│         return;
 449│     }
 450│

(gdb) p v
$1 = QList<QVariant> (size = 0)