origin-dollar: Large mint causes revert on fork

To reproduce: Terminal A

export BLOCK_NUMBER=...
export PROVIDER_URL="https://eth-mainnet.alchemyapi.io/v2/..."
yarn run node:fork

Terminal B

FORK=true npx hardhat fund --index 4 --num 1 --amount 1000000 --network localhost
FORK=true npx hardhat mint --index 4 --num 1 --amount 50000 --network localhost

Minting 50000 OUSD for account 4 at address 0x1974f84881Af4204a21f18c43D7c4d9Dee331Bb5
An unexpected error occurred:

ProviderError: Transaction reverted without a reason
    at HttpProvider.request (/Users/franck/src/origin-dollar/contracts/node_modules/hardhat/src/internal/core/providers/http.ts:45:19)
    at GanacheGasMultiplierProvider.request (/Users/franck/src/origin-dollar/contracts/node_modules/hardhat/src/internal/core/providers/gas-providers.ts:170:34)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)

A smaller mint (ex 1k) succeeds, so this is likely a failure in allocate().

Possibly related to https://github.com/trufflesuite/ganache-core/issues/571