This is the only sensible criticism of Russia's actions from China's perspective. A weakened European economy will hurt China to some extent, as will the higher oil and gas prices.NS2 is not only to serve Germany but part of EU around Germany. If this part of EU has problem to pay their electricity bill for basic heating and cocking let alone factories to make some money, how are they going to pay for Chinese import? Wishing to crash competitors in this manner is like "killing the hen for the egg".
Also a down-falling Germany will only benefit the American puppets in Europe, such as UK. It is the worst thing for China. Basically the US and UK etc. are actively pursuit the fall of any big powers who want to be independent or neutral, like Germany and France etc.
However, Europe's undoing will be the result of it's failure to develop an independent foreign policy. They could have used the last 8 years to force Ukraine to deal with the separatist issue politically. If the EU had put sanctions on Ukraine for restrictions on native Russian speakers, prosecution of war criminals and dissolution of the neo-nazi Azov branch of the Ukrainian military this conflict would have been over.
Instead they allowed their policy to be dictated by Americans, and actually encouraged Ukrainian belligerence by dangling the carrot of EU membership in front of them.
The same European apparatus will be used against China. Hopefully after this episode the Europeans will learn that following American policy blindly comes at a cost. So in the long term, a weak Europe is good for China.