Gaza has a sizable coastline, and China has a large number of amphibious assault ships available. They can defend themselves against Israel air attacks. If China decides to send humanitarian relief to Gaza, China can do it, and Israel can't stop them.[3] China would look like the good guys. Which their leadership knows.
[1] https://www.foreignaffairs.com/china/chinas-game-gaza
[2] https://edition.cnn.com/middleeast/live-news/israel-hamas-wa...
[3] https://www.newsweek.com/china-amphibious-assault-ship-type-...
Additionally china's military currently has big corruption problems (e.g. the missle fuel water controversy). I doubt china really wants to put their reputation on the line until they sort that out, especially given what happened to russia in ukraine.