Submitted by WatchPug, also found by 0x52
https://github.com/code-423n4/2022-05-backd/blob/2a5664d35cde5b036074edef3c1369b984d10010/protocol/contracts/tokenomics/Minter.sol#L104-L108
As lastEvent and lastInflationDecay are not initialized in the constructor(), they will remain to the default value of 0.
However, the permissionless executeInflationRateUpdate() method does not check the value of lastEvent and lastInflationDecay and used them directly.
As a result, if executeInflationRateUpdate() is called before startInflation():
https://github.com/code-423n4/2022-05-backd/blob/2a5664d35cde5b036074edef3c1369b984d10010/protocol/contracts/tokenomics/Minter.sol#L115-L117
https://github.com/code-423n4/2022-05-backd/blob/2a5664d35cde5b036074edef3c1369b984d10010/protocol/contracts/tokenomics/Minter.sol#L187-L215
https://github.com/code-423n4/2022-05-backd/blob/2a5664d35cde5b036074edef3c1369b984d10010/protocol/contracts/tokenomics/Minter.sol#L50-L51
https://github.com/code-423n4/2022-05-backd/blob/2a5664d35cde5b036074edef3c1369b984d10010/protocol/contracts/tokenomics/Minter.sol#L217-L227
Consider initializing lastEvent, lastInflationDecay in constructor().
or
Consider adding require(lastEvent != 0 && lastInflationDecay != 0, "...") to executeInflationRateUpdate().
danhper (Backd) confirmed 
Alex the Entreprenerd (judge) commented:
