Bugfixes concerning UniqID and select on abtract LeObject child

lodel/leapi/lefactory.py

 )
         res += em_cls_code
         # Dyncode fields bootstrap instructions
+        child_classes = model.get_class_childs(em_class.uid)
+        if len(child_classes) == 0:
+            child_classes = 'tuple()'
+        else:
+            child_classes = '(%s,)' % (', '.join(
+                [ LeObject.name2objname(emcls.uid) for emcls in child_classes]))
         bootstrap += """{classname}._set__fields({fields})
 {classname}._child_classes = {child_classes}
 """.format(
     classname = LeObject.name2objname(em_class.uid),
     fields = '{' + (', '.join(['\n\t%s: %s' % (repr(emfield.uid),data_handler_constructor(emfield)) for emfield in em_class.fields()])) + '}',
-    child_classes = '(' + (', '.join([ LeObject.name2objname(emcls.uid) for emcls in model.get_class_childs(em_class.uid)]))+ ')',
+    child_classes = child_classes,
 )
     bootstrap += "\n"
     return res, set(imports), bootstrap

plugins/mongodb_datasource/datasource.py

         tuid = target._uid[0] # Multiple UID broken here
         results = self.select(
             target, [tuid], [], order=[(tuid, 'DESC')], limit = 1)
+        if len(results) == 0: 
+            return 1
         return results[0][tuid]+1
 
     ##@brief returns a selection of documents from the datasource
         if target.is_abstract():
             target_childs = target.child_classes()
             for target_child in target_childs:
-                results.append(self.select(target=target_child, field_list=field_list, filters=filters,
-                                           rel_filters=rel_filters, order=order, group=group, limit=limit,
-                                           offset=offset))
+                results += self.select(
+                    target=target_child, field_list=field_list,
+                    filters=filters, rel_filters=rel_filters, order=order,
+                    group=group, limit=limit, offset=offset)
         else:
             # Default arg init
             filters = [] if filters is None else filters