fix: Forbid the addition of 0 to 9 items

[amuyu]

If you turn the screen off during pagination and turn it on for a while, the item is added from 0 to 9.
Like this,

Item 0
Item 1
Item 3
Item 4
Item 5
Item 6
Item 7
Item 8
Item 9
Item 0
Item 1
Item 2
Item 3
Item 4
Item 5
Item 6
Item 7
Item 8
Item 9
Item 20
Item 21
Item 22
Item 23
Item 24
Item 25
Item 26
Item 27
Item 28
Item 29

The reason is that _paginator.onNext(0) is called in onStart when the screen is on.
If emit the number of the list in onStart, it display normally.