Why is China entering a nuclear security pact with Ukraine?

Yu Ligong, Want China Times (China)
China promises unconditionally not to use or threaten to use nuclear weapons against non-nuclear Ukraine, and to provide security guarantees to Ukraine if Ukraine is attacked by nuclear weapons or threatened by such aggression. Clearly, this is a guarantee for strategic alliance and an unusual nuclear protection umbrella. Ukraine is far from China and in no way affects the latter's national security. What,then, is the need for such an agreement?