AddressBook.sol

[jovinkassi]

pragma solidity 0.5.10;

contract AddressBook {

//maps an address to an address array
//As an example your address to a list of addresses you are interested in.  This supports multiple people having an address book

mapping(address => address[]) private _addresses;


//maps an address to another map of address to a string
//example - your address mapped to a mapping of your address book to its alias

mapping(address => mapping(address => string)) private _aliases;


//returns the list of addresses in the _addresses map
function getAddressArray(address addr) public returns (address[] memory) {
    return _addresses[addr];
}

//adds address to your list of addresses in the _addresses map.
//Uses push since it is an array
//adds your address, address and alias to the _aliases map
function addAddress(address addr, string memory alia) public {
    _addresses[msg.sender].push(addr);
    _aliases[msg.sender][addr] = alia;
}

function removeAddress(address addr) public {
    // get the length of the addresses in the array from the msg sender
    uint length = _addresses[msg.sender].length;
    for(uint i = 0; i < length; i++) {
        // if the address that you want to remove = one of the addresses you own 
        //and is one of the iterations of the loop
        if (addr == _addresses[msg.sender][i]) {
            //once we find the item in the array we need to delete the item
            //then shift each item down 1.  You can't just delete an item in the middle of an array
            //make sure the length of the address is not < 1 (this is needed because we are going to reorder the array)
            if(1 < _addresses[msg.sender].length && i < length-1) {
                //shift the last item in the array to the position of the item that we are removing
                _addresses[msg.sender][i] = _addresses[msg.sender][length-1];
            }

            // delete the item we just swapped from
            delete _addresses[msg.sender][length-1];
            //then decrement the length of the array by 1
            _addresses[msg.sender].length--;
            //delete the alias for it
            delete _aliases[msg.sender][addr];
            //_state[msg.sender]++;
            break;
        }
    }
}

//Gets the alias for your address
function getAlias(address addrowner, address addr) public returns (string memory) {
    return _aliases[addrowner][addr];
} 

}

i tried running the above code but not working,,error:cant decrement length