hello everyone,
I'm trying to compile a simple contract on VSCODE with Openzeppelin.
this is the source code of the contract -
#####################################
pragma solidity >= 0.6.0 < 0.9.0;

import "D:/ShlavB/TestCon/node_modules/@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "D:/ShlavB/TestCon/node_modules/@openzeppelin/contracts/access/ownable.sol";

contract TestCon is ERC20, Ownable {
address public admin;
uint private limit = 0;
string token_name = 'TestCon';
string token_symbol = 'TTC';
uint256 token_totalSupply = 1000000;


constructor()public ERC20(token_name, token_symbol) {
admin = owner();
transferOwnership(admin);
_mint(admin, token_totalSupply * 10 ** uint256(18));
}

function getLimit() public view returns(uint){
return limit;
}

function setLimit(uint val) public {
require(
msg.sender == admin,
"No access"
);
limit = val;
}
}
###################################################

I'm getting the following error message -
✖️ Compiling contracts with solc 0.8.4 (commit.c7e474f2)
Compilation warnings:
Warning: SPDX license identifier not provided in source file. Before publishing, consider adding a comment containing "SPDX-License-Identifier: " to each source file. Use "SPDX-License-Identifier: UNLICENSED" for non-open-source code. Please see https://spdx.org for more information.
--> contracts\TestCon.sol


Warning: Visibility for constructor is ignored. If you want the contract to be non-deployable, making it "abstract" is sufficient.
--> contracts\TestCon.sol:14:5:
|
14 | constructor()public ERC20(token_name, token_symbol) {
| ^ (Relevant source part starts here and spans across multiple lines).

Cannot convert undefined or null to object

Does anyone have idea why is it happening?