Is it possible to use arrayformula to copy the values above if the cell on its left is empty?

I'm trying to populate a column (Cell C2) with the value of the cell in the column to its left (Cell B2) if B2 is not empty; if B2 is empty, then C2 equals to C1.

If B3 is not empty, then C3 equals to B3; if B3 is empty, C3 equals C2.

I try using an array formula, but it returns circular reference error. And I certainly can't use INDEX and INDIRECT either.

Please help.

The sample file:

https://docs.google.com/spreadsheets/d/1TXz5m5LtTF632bMrwIIDlO-4NMavgs6HA4FE8_BFhRs/edit?usp=sharing