Blank required form fields not detected

In the process of investigating http://drupal.org/node/35467, I found that blank required form fields are not detected anymore.

I think the problem is in form.inc:

@@ -138,7 +138,7 @@ function _form_validate($elements) {
 
   /* Validate the current input */
   if (!$elements['#validated'] && $elements['#input']) {
*    if ($elements['#required'] && !isset($elements['#value'])) {
         form_error($elements, t('%name field is required', array('%name' => $elements['#title'])));
     }
     if ($elements['#valid']) {

The !isset does not work for a field that is blank. I tried replacing it with empty(), which works most of the time but empty() also returns TRUE for a string "0" and a integer 0.

I created a new function drupal_empty() to replace the !isset

function drupal_empty($value = NULL) {
  if (isset($value)) {
    if (empty($value) && ($value !== 0) && ($value !== '0'))
      return TRUE;
    else
      return FALSE;
  }
  else
    return TRUE;
}

(it's not optimised or anything, just copied from the php help)

And that seems to work for the required form fields and '0' string fields are handled properly.

Is this the best course of action? Are there other places in the code which don't work quite right because of isset()/empty() which could also use a function like this?