Gas estimation errored with the following message... Error: gas required exceeds allowance or always failing transaction

I made a smart contract, but i got an error while deploying it , after i specified the Gas limit of 3000000 and a random value (wei) , and clicking on Create , i got the following error :

( i am using Remix IDE , Metatmask extension and Ropsten the network . I have 10 Eth in my balance and I tried with solidity compiler 0.4.9 and 0.4.20 as well but still getting the same error)

Error :

Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? Error: gas required exceeds allowance or always failing transaction at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:1391377 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:927906 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:346093 at o (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:364324) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:348923 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:346093 at c (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:349199) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:349237 at Ht (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:358606) at Object.<anonymous> (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:349326) at e.value (chrome- 

This my code :

pragma solidity ^0.4.21; contract admined{ address public admin; function admined(){ admin = msg.sender; } modifier onlyAdmin(){ require(msg.sender == admin); _; } function transferAdminRol(address newAdmin)public onlyAdmin { admin = newAdmin; } } contract ERC20{ mapping(address => uint256) public balanceOf; mapping(address => mapping(address => uint256)) public allowance; string public standard = "Test Africa v0.1"; string public name; string public symbol; uint8 public decimal; uint256 public totalSupply; event Transfer(address indexed from, address indexed to, uint256 value); event Approval(address indexed owner, address indexed spender, uint256 value); function ERC20(uint256 initialSupply, string _name, string _symbol, uint8 _decimal) public{ balanceOf[msg.sender] = initialSupply; name = _name; symbol = _symbol; decimal = _decimal; totalSupply = initialSupply; } function transfer(address _to, uint256 _value)public returns (bool success){ require(balanceOf[msg.sender] >= _value); require(balanceOf[_to] + _value >= balanceOf[_to]); balanceOf[msg.sender] -= _value; balanceOf[_to] += _value; emit Transfer(msg.sender, _to, _value); return true; } function approve(address _spender, uint256 _value) public returns (bool success){ allowance[msg.sender][_spender] = _value; emit Approval(msg.sender, _spender, _value); return true; } function allowance(address _owner, address _spender) public returns (uint256 remaining) { return allowance[_owner][_spender]; } function transferFrom(address _from, address _to, uint256 _value)public returns (bool success){ require(balanceOf[_from] >= _value); require(balanceOf[_to] + _value >= balanceOf[_to]); require(_value <= allowance[_from][msg.sender]); balanceOf[_from] -= _value; balanceOf[_to] += _value; allowance[_from][msg.sender] -= _value; emit Transfer(_from, _to, _value); return true; } function balanceOf(address _owner)public constant returns (uint256 balance) { return balanceOf[_owner]; } } contract testaAFC is admined, ERC20{ uint public minBalanceForAccounts = 50000000000000 wei; uint256 public sellPrice = 500; uint256 public buyPrice = 500; bytes32 public currentChallenge; uint public timeOfLastProof; uint public difficulty = 10**32; mapping (address => bool) public frozenAccount; event FrozenFunds(address target, bool frozen); function testaAFC(uint256 initialSupply, string _name, string _symbol, uint8 _decimal, address _admin)public ERC20(0, _name, _symbol, _decimal){ if(_admin != 0) admin = _admin; else admin = msg.sender; balanceOf[admin] = initialSupply; totalSupply = initialSupply; } function transfer(address _to, uint256 _value)public returns (bool success){ // } function transferFrom(address _from, address _to, uint256 _value)public returns (bool success){ // } function setMinBalance(uint minimumBalanceInFinney)public onlyAdmin { minBalanceForAccounts = minimumBalanceInFinney * 1 wei; } function mintToken(address target, uint256 mintedAmount)public onlyAdmin { balanceOf[target] += mintedAmount; totalSupply += mintedAmount; emit Transfer(0, this, mintedAmount); emit Transfer(this, target, mintedAmount); } function setPrices(uint256 newSellPrice, uint256 newBuyPrice)public onlyAdmin { sellPrice = newSellPrice; buyPrice = newBuyPrice; } function buy()public payable returns (uint amount){ amount = msg.value * buyPrice; require(balanceOf[this] >= amount); balanceOf[msg.sender] += amount; balanceOf[this] -= amount; emit Transfer(this, msg.sender, amount); return amount; } function sell(uint amount)public returns (uint revenue){ require(balanceOf[msg.sender] >= amount); balanceOf[this] += amount; balanceOf[msg.sender] -= amount; revenue = amount / sellPrice; msg.sender.transfer(revenue); emit Transfer(msg.sender, this, amount); return revenue; } } 

PLEASE HELP I'M IN A RUSH THANKS !!!