I'll suggest changing line 536 of paypalwpp.php to reflect the change made for zc157a:
Code:
                          'settle_amount' => (float)(isset($this->responsedata['PAYMENTINFO_0_SETTLEAMT']) ? urldecode($this->responsedata['PAYMENTINFO_0_SETTLEAMT']) : $this->amt),
Note the subtle difference between that and zc157, the movement of the closing parentheses from after the isset() clause to after the $this->amt element.