Fix crash in container_descendants()
Fix crash in container_descendants()

If root is a C_VIEW, the children property is a null pointer.

1ace/sway,taiyu-len/sway,ascent12/sway,taiyu-len/sway,SirCmpwn/sway,taiyu-len/sway,1ace/sway,ascent12/sway,1ace/sway,ascent12/sway