Wordpress PHP Shortcode if isset pulling through for all shortcodes on page

Question

When using this shortcode on page multiple times, every shortcode gets the output of the addpad class and the inline style. How do I do this so only the shortcode that has the attributes will output the code?

function block_one_third( $atts, $content = null ) {
   extract(shortcode_atts(array(
      'bg' => '',
      'text' => '',
   ), $atts));
   if (isset($bg) || isset($text)){ $style = ' style="background-color:'. $bg .';color:'. $text .'"';}
   if (isset($bg) || isset($text)) { $padit = ' addpad'; }
   return '<div class="one_third'. $padit .'"'. $style .'>' . do_shortcode($content) . '</div>';
}
add_shortcode('one_third', 'block_one_third');

[one_third]
Block 1 - Should have NO additional class or inline style
[/one_third]
[one_third bg="red"]
Block 2 WITH additional html output
[/one_third]
[one_third_last]
Block 3 - Should have NO additional class or inline style
[/one_third_last]

Answer 1

Technically, isset($bg) will return true because in these lines, you specify a default for $bg if it isn't set:

extract(shortcode_atts(array(
  'bg' => '', // $bg default is '' if it wasn't found
  'text' => '', // $text default is '' if it wasn't found
), $atts));

Instead of checking if it is set, check if it equals your default value:

if (strcmp($bg,'') == 0 || strcmp($text,'') == 0 ) {
    // Do Something
}