Use None instead of False when calling fields_get for import/export for issue759

tryton/gui/window/win_export.py

@@ -210,7 +210,7 @@ class WinExport(object):
                 if fields[field].get('relation', False) and level>0:
                     try:
                         fields2 = rpc.execute('object', 'execute',
-                                fields[field]['relation'], 'fields_get', False,
+                                fields[field]['relation'], 'fields_get', None,
                                 rpc.CONTEXT)
                     except Exception, exception:
                         common.process_exception(exception, self.parent)

tryton/gui/window/win_import.py

@@ -224,7 +224,7 @@ class WinImport(object):
                         try:
                             fields2 = rpc.execute('object',
                                     'execute', fields[field]['relation'],
-                                    'fields_get', False, rpc.CONTEXT)
+                                    'fields_get', None, rpc.CONTEXT)
                         except Exception, exception:
                             common.process_exception(exception, self.dialog)
                             continue