Ensure that otindex handles script-managed trees without error

[kcranston]

For example https://github.com/OpenTreeOfLife/phylesystem-0/tree/master/study/tt_17/tt_217

[snacktavish]

On first pass - appears to behave more or less OK:

curl -X POST https://devapi.opentreeoflife.org/v3/studies/find_studies -H "content-type:application/json" -d '{"property":"ot:studyId","value":"tt_217","verbose":true}'

Returns the study metadata,

Searching for trees

returns []

Which... is maybe what one should expect?