if (chunks === null) return null; // End of stream
A block has a storage capacity, and once it's used up, it can be closed and linked to a previously served block.
，这一点在爱思助手下载最新版本中也有详细论述
第一百一十一条 公安机关查处治安案件，对没有本人陈述，但其他证据能够证明案件事实的，可以作出治安管理处罚决定。但是，只有本人陈述，没有其他证据证明的，不能作出治安管理处罚决定。
NASA also moved up the launch of Crew-12 to replace the prematurely-returned astronauts. That team docked at the ISS on February 14 and are scheduled to stay on the space station for around eight months.