Check that the bond is listed before opening a vault

[Paul Razvan Berg]

Without this check, ghost vaults can be created:

hifi-protocol/contracts/BalanceSheet.sol

Lines 522 to 528 in 8904b7f

 function openVault(FyTokenInterface fyToken) external override returns (bool) { 
     require(fyToken.isFyToken(), "ERR_OPEN_VAULT_FYTOKEN_INSPECTION"); 
     require(vaults[address(fyToken)][msg.sender].isOpen == false, "ERR_VAULT_OPEN"); 
     vaults[address(fyToken)][msg.sender].isOpen = true; 
     emit OpenVault(fyToken, msg.sender); 
     return true; 
 } 

[Paul Razvan Berg]

This may require a new function getBondListed in the Fintroller.

[Paul Razvan Berg]

Implemented in e7ea749.

Added a new function isBondListed.