local:local metdata bug value

[syphax-bouazzouni]

Issue

When we send the following path request to http://data.stageportal.lirmm.fr/ontologies/ANAEETHES/submissions/1

{
  "useImports": [""]
}

it saves the following

{
  "useImports": ["local:local"]
}

The problem is in multiple levels

1. UI: sending "useImports": [""] if empty instead of "useImports": [ ]
2. GOO: for "useImports": [""] saved in the triple store but the mapper returns "useImports": ["local:local"]

TODO

• Fix the submission form sending empty string when nothing is set instead of nil or empty arrays bioportal_web_ui#89

• Fix the saver of empty URI returning local:local goo#11 (will be let for later/never)