[#61] Added the case of a non given relational_filters argument

leobject/datasources/ledatasourcesql.py

     # @param emtype
     # @param filters list : list of tuples formatted as (FIELD, OPERATOR, VALUE)
     # @param relational_filters
-    def get(self, emclass, emtype, field_list, filters, relational_filters):
+    def get(self, emclass, emtype, field_list, filters, relational_filters=None):
 
         tablename =  emclass.name
         where_filters = self._prepare_filters(filters)
-        rel_filters = self._prepare_filters(relational_filters)
+        if relational_filters or len(relational_filters) > 0:
+            rel_filters = self._prepare_filters(relational_filters)
         query = select(tablename, where=where_filters, select=field_list)
         self.db.execute(query)
+
         return all_to_dicts(self.db)
 
     # @brief prepares the filters to be used by the mosql library's functions