> The story was reported in China but is tricky to find. Sina (Chinese language), rough translation.
  > ...

The original Chinese title of Sina report:

  > 中国承诺为乌克兰提供核保护伞？假！

Translation:

  > China pledges nuclear umbrella for Ukraine? It's false!

And in later paragraphs the Sina report distinguishes "security assurance" from "nuclear umbrella" by explaining the concepts of positive and negative security assurances and citing multiple documents including UNSC resolution 255.

So it is reported by Chinese media like an ordinary statement on non-nuclear-weapon countries according to UN resolutions.