per Fred

taipy/gui/gui.py

@@ -31,7 +31,7 @@
 
 import markdown as md_lib
 import tzlocal
-from flask import Blueprint, Flask, g, has_app_context, jsonify, request, send_file, send_from_directory
+from flask import Blueprint, Flask, g, has_app_context, has_request_context, jsonify, request, send_file, send_from_directory
 from werkzeug.utils import secure_filename
 
 import __main__  # noqa: F401
@@ -1003,7 +1003,11 @@ def __send_var_list_update(  # noqa C901
                     newvalue = newvalue.get()
                 if isinstance(newvalue, (dict, _MapDict)):
                     # Skip in taipy-gui, available in custom frontend
-                    if request.cookies.get(_Server._RESOURCE_HANDLER_ARG, None) is None:
+                    resource_handler_id = None
+                    with contextlib.suppress(Exception):
+                        if has_request_context():
+                            resource_handler_id = request.cookies.get(_Server._RESOURCE_HANDLER_ARG, None)
+                    if resource_handler_id is None:
                         continue  # this var has no transformer
                 if isinstance(newvalue, float) and math.isnan(newvalue):
                     # do not let NaN go through json, it is not handle well (dies silently through websocket)