Little gap between container's border and background of a child element (CHROME)

.login-modal {
    background: white;
    box-sizing: border-box;
    --main-bg-color: rgb(70, 119, 139);
    display: grid;
    /* grid-auto-rows: minmax(20px, auto); */
    grid-auto-columns: minmax(120px, 180px);
    top: 10px;
    position: absolute;
    left: 50%;
    transform: translate(-50%);
    overflow: hidden;
    border-radius: 7px;
    color: var(--main-bg-color);
    font-family: "Open Sans", sans-serif;
    border: 1px solid var(--main-bg-color);
    z-index: 1999;
  }


  #login-window-small.login-modal ul {
    padding: 0;
    margin: 0;
  }

  #login-window-small.login-modal li {
    list-style-type: none;
    margin: .5em;
  }

  #login-window-small.login-modal a {
    text-decoration: none;
    color: var(--main-bg-color);
  }

  .modal-head {
    display: flex;
    align-items: center;
    color: white;
    position: relative;
    background-color: var(--main-bg-color);
  }

  .modal-head>span {
    margin-left: 1em;
  }

  .modal-form {
    margin-top: 1em;
  }

  .modal-form label {
    margin: .5em 0;
  }

  .modal-social-links {
    grid-column: 1/3;
    display: flex;
    margin: 0 0 2em 1em;

  }

  .form {
    display: flex;
    flex-direction: column;
    font-size: 16px;
    margin: 0 1em;
  }

  .form input[type="password"],
  .form input[type="text"] {
    height: 2em;
    font-size: 16px;
    border: 1px solid #aaa;
    border-radius: 3px;
    padding-left: 5px;
  }

  #login-window-small .form a {
    display: flex;
    justify-content: flex-end;
    cursor: pointer;
  }

  #login-window-small .form a>span {
    color: rgb(250, 91, 15);
  }


  .modal-head {
    grid-row: 1/3;
    height: 4em;
  }

  .modal-head,
  .modal-form {
    grid-column: 1/3;
  }

  .modal-buttons-cont {
    display: flex;
    justify-content: center;

  }

  .modal-buttons-cont button {
    border: 1px solid var(--main-bg-color);
    border-radius: .2em;
    padding: .5em 1.5em;
    font-size: 18px;
    cursor: pointer;
  }

  .modal-buttons-cont.close {
    grid-column: 1;
    opacity: unset;
  }

  .modal-buttons-cont.signin {
    grid-column: 2;
  }

  .modal-buttons-cont.close button {
    color: var(--main-bg-color);
    background-color: white;
  }

  .modal-buttons-cont.close button:hover {
    background-color: #ebebeb;
  }

  .modal-buttons-cont.signin button {
    color: white;
    background-color: var(--main-bg-color);
  }

  .modal-buttons-cont.signin button:hover {
    background-color: rgb(50, 99, 119);
  }

  .bottom-padd {
    grid-column: 1/3;
    grid-row: 6;
    height: 2em;
  }

  .message-cont {
    padding: 1em 2em;
  }

  .message-cont span {
    color: red;
  }

<div id="login-window-small" class="login-modal">
  <div class="modal-head"><span>Member Sign In</span></div>
  <div class="modal-form">
    <form class="form" action="post">
      <label for="uname"><b>Username</b></label>
      <input id="username-input" type="text" placeholder="Enter Username" name="uname" required>
      <label for="psw"><b>Password</b></label>
      <input id="password-input" type="password" placeholder="Enter Password" name="psw" required>
      <label>
        <input type="checkbox" checked="checked" name="remember"> Remember me
      </label>
      <a> <span>Lost Password</span> </a>
    </form>
  </div>
  <div class="modal-social-links">
    <ul>
      <li><a href="">Fecebook</a></li>
      <li><a href="">Twitter</a></li>
      <li><a href="">Linkedin</a></li>
    </ul>
  </div>
  <div class="modal-buttons-cont close">
    <button>Close</button>
  </div>
  <div class="modal-buttons-cont signin">
    <button>Sign In</button>
  </div>
  <div class="bottom-padd">
    <div class="message-cont">
      <span></span>
    </div>
  </div>
</div>