Submitted by hack3r-0m, also found by defsec
 oracle can 0 as a price of the share, in that case, 0 will be the denominator in some calculations which can cause reverts from SafeMath (for e.g here: WrappedIbbtc.sol L148) resulting in Denial Of Service.
Add a null check to ensure that on every update, the price is greater than 0.
dapp-whisperer (BadgerDAO) confirmed:
