Context

I'm migrating my docs repo. And was tried to use mkdocs with material theme to build blog somewhat. I use obsidian as the editor. And the default metadata's tags will be empty. Also that I level it empty in most files.
Which looks like:

Author: "@godot42"
Date: "{{date}} {{time}}"
pub: false
pub-category:
tags:

But as I enabled the tags plugin, empty tags section will be considered as a exception.

Bug description

The error messages and traceback:
ERROR - Error building page 'Arc/Game/ECS_With_UI.md': 'NoneType' object is not iterable
Traceback (most recent call last):
File "C:\Users\norm\miniconda3\lib\runpy.py", line 197, in _run_module_as_main
return _run_code(code, main_globals, None,
File "C:\Users\norm\miniconda3\lib\runpy.py", line 87, in run_code
exec(code, run_globals)
File "C:\Users\norm\miniconda3\Scripts\mkdocs.exe_main.py", line 7, in
File "C:\Users\norm\miniconda3\lib\site-packages\click\core.py", line 1157, in call
return self.main(*args, **kwargs)
File "C:\Users\norm\miniconda3\lib\site-packages\click\core.py", line 1078, in main
rv = self.invoke(ctx)
File "C:\Users\norm\miniconda3\lib\site-packages\click\core.py", line 1688, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "C:\Users\norm\miniconda3\lib\site-packages\click\core.py", line 1434, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "C:\Users\norm\miniconda3\lib\site-packages\click\core.py", line 783, in invoke
return _callback(*args, **kwargs)
File "C:\Users\norm\miniconda3\lib\site-packages\mkdocs_main.py", line 270, in serve_command
serve.serve(**kwargs)
File "C:\Users\norm\miniconda3\lib\site-packages\mkdocs\commands\serve.py", line 86, in serve
builder(config)
File "C:\Users\norm\miniconda3\lib\site-packages\mkdocs\commands\serve.py", line 67, in builder
build(config, live_server=None if is_clean else server, dirty=is_dirty)
File "C:\Users\norm\miniconda3\lib\site-packages\mkdocs\commands\build.py", line 349, in build
_build_page(
File "C:\Users\norm\miniconda3\lib\site-packages\mkdocs\commands\build.py", line 222, in _build_page
context = config.plugins.on_page_context(context, page=page, config=config, nav=nav)
File "C:\Users\norm\miniconda3\lib\site-packages\mkdocs\plugins.py", line 583, in on_page_context
return self.run_event('page_context', context, page=page, config=config, nav=nav)
File "C:\Users\norm\miniconda3\lib\site-packages\mkdocs\plugins.py", line 507, in run_event
result = method(item, **kwargs)
File "C:\Users\norm\miniconda3\lib\site-packages\material\plugins\tags\plugin.py", line 117, in on_page_context
context["tags"] = [
TypeError: 'NoneType' object is not iterable

Related links

• Reporting a bug

Reproduction

9.5.18-tags_plugins_exception.zip

Steps to reproduce

Run mkdocs when tags of metadata is empty

Browser

No response

Before submitting

• I have read and followed the bug reporting guidelines.
• I have attached links to the documentation, and possibly related issues and discussions.
• I assure that I have removed all customizations before submitting this bug report.
• I have attached a .zip file with a minimal reproduction using the built-in info plugin.