There's been a bug in the email-archive tool's "re-send email" option that causes that error.
The only known bug in functions_email.php is on line 366:
Code:
if (!defined($block['EXTRA_INFO'])) $block['EXTRA_INFO'] = '';
should be:
Code:
if (!isset($block['EXTRA_INFO'])) $block['EXTRA_INFO'] = '';
... but that shouldn't cause a fatal error.
You could try changing line 323 from this:
Code:
if ($block == '' && !is_array($block)) $block = array();
to this:
Code:
if ($block == '' or !is_array($block)) $block = array();
... would be curious to know if this edit makes any difference (since this is intended to be a safety-catch to protect against the bug in the email archive re-send tool).