@mixin _google-font($family, $styles: (), $protocol: null) {

  $url: "//fonts.googleapis.com/css?family=";

  @if $protocol {
    $url: _str-prepend($url, $protocol + ":");
  }

  @if type-of($family) == string {
    $family: _split($family, " ");
  }
  $family: _str-join($family, "+");

  $url: _str-append($url, $family);

  @if length($styles) != 0 {
    $url: _str-append($url, ":");

    $url: _str-append($url, _str-join($styles));
  }
  @import url(quote($url));
}

@mixin _google-font($family, $styles: (), $protocol: null) {

  $url: "//fonts.googleapis.com/css?family=";

  @if $protocol {
    $url: _str-prepend($url, $protocol + ":");
  }

  @if type-of($family) == string and _str-contains($family, " ") {
    $family: _split($family, " ");
  }
  $family: _str-join($family, "+");

  $url: _str-append($url, $family);

  @if length($styles) != 0 {
    $url: _str-append($url, ":");

    $url: _str-append($url, _str-join($styles));
  }
  @import url(quote($url));
}

Check if $family contains space
Check if $family contains space
