always return true or false for sharemetadata

oml/item/models.py

@@ -141,6 +141,7 @@ class Item(db.Model):
         for key in self.array_keys:
             if key in j and not isinstance(j[key], list):
                 j[key] = [j[key]]
+        j['sharemetadata'] = j.get('sharemetadata', False)
         return j
 
     def get_path(self):