Access to assimilators does not check for existence and allows delegation to the zeroth address
For every method that allows to selectively withdraw, deposit, or swap tokens in `Loihi`, the user is allowed to specify addresses for the assimilators of said tokens (by inputting the addresses of the tokens themselves).\\nThe shell then performs a lookup on a mapping called `assimilators` inside its main structure and uses the result of that lookup to delegate call the assimilator deployed by the shell administrator.\\nHowever, there are no checks for prior instantiation of a specific, supported token, effectively meaning that we can do a lookup on an all-zeroed-out member of that mapping and delegate call execution to the zeroth address.\\nFor example, the 32 bytes expected as a result of this call:\\n```\\nfunction viewNumeraireAmount (address \\_assim, uint256 \\_amt) internal returns (int128 amt\\_) {\\n\\n    // amount\\_ = IAssimilator(\\_assim).viewNumeraireAmount(\\_amt); // for production\\n\\n    bytes memory data = abi.encodeWithSelector(iAsmltr.viewNumeraireAmount.selector, \\_amt); // for development\\n\\n    amt\\_ = abi.decode(\\_assim.delegate(data), (int128)); // for development\\n\\n}\\n```\\n\\nThis is definitely an insufficient check since the interface for the assimilators might change in the future to include functions that have no return values.
Check for the prior instantiation of assimilators by including the following requirement:\\n`require(shell.assimilators[<TOKEN_ADDRESS>].ix != 0);`\\nIn all the functions that access the `assimilators` mapping and change the indexes to be 1-based instead pf 0-based.
```\\nfunction viewNumeraireAmount (address \\_assim, uint256 \\_amt) internal returns (int128 amt\\_) {\\n\\n    // amount\\_ = IAssimilator(\\_assim).viewNumeraireAmount(\\_amt); // for production\\n\\n    bytes memory data = abi.encodeWithSelector(iAsmltr.viewNumeraireAmount.selector, \\_amt); // for development\\n\\n    amt\\_ = abi.decode(\\_assim.delegate(data), (int128)); // for development\\n\\n}\\n```\\n