Iridium Module - Blank Page - Debug Error

[katea]

This is the full code for that section:

		$confirmation['fields'][] = array(
				'title' => MODULE_PAYMENT_IRIDIUM_TEXT_CARD_NUMBER,
				'field' => substr($this->card_number, 0, 4) .
					str_repeat('X', (strlen($this->card_number) - 8)) .
					substr($this->card_number, -4)
			);

[katea]

Oops, seems to be one more:

PHP Warning:  str_repeat() [<a href='function.str-repeat'>function.str-repeat</a>]: Second argument has to be greater than or equal to 0 in /home/sites/mysite.com/public_html/includes/modules/payment/iridium.php on line 1322

Different line but exactly the same code from line 1213 ..

This is the full code for this part:

// Store the card details for this order
			// Hide middle digits for the card number
			$order->info['cc_number'] = substr($_POST['card_number'], 0, 4) .
				str_repeat('X', (strlen($_POST['card_number']) - 8)) .
				substr($_POST['card_number'], -4);

[katea]

No-one? Surely someone has had this problem?

Please help!