fixed typos for zero ordertotal creditmemo feature

app/code/Magento/Sales/Model/Order.php

@@ -656,8 +656,8 @@ private function canCreditmemoForZeroTotalRefunded($totalRefunded)
         $isRefundZero = abs($totalRefunded) < .0001;
         // Case when Adjustment Fee (adjustment_negative) has been used for first creditmemo
         $hasAdjustmentFee = abs($totalRefunded - $this->getAdjustmentNegative()) < .0001;
-        $hasActinFlag = $this->getActionFlag(self::ACTION_FLAG_EDIT) === false;
-        if ($isRefundZero || $hasAdjustmentFee || $hasActinFlag) {
+        $hasActionFlag = $this->getActionFlag(self::ACTION_FLAG_EDIT) === false;
+        if ($isRefundZero || $hasAdjustmentFee || $hasActionFlag) {
             return false;
         }
 
@@ -676,13 +676,12 @@ public function canCreditmemoForZeroTotal($totalRefunded)
         //check if total paid is less than grandtotal
         $checkAmtTotalPaid = $totalPaid <= $this->getGrandTotal();
         //case when amount is due for invoice
-        $dueAmountCondition = $this->canInvoice() && ($checkAmtTotalPaid);
+        $hasDueAmount = $this->canInvoice() && ($checkAmtTotalPaid);
         //case when paid amount is refunded and order has creditmemo created
-
         $creditmemos = ($this->getCreditmemosCollection() === false) ?
              true : (count($this->getCreditmemosCollection()) > 0);
         $paidAmtIsRefunded = $this->getTotalRefunded() == $totalPaid && $creditmemos;
-        if (($dueAmountCondition || $paidAmtIsRefunded) ||
+        if (($hasDueAmount || $paidAmtIsRefunded) ||
             (!$checkAmtTotalPaid &&
             abs($totalRefunded - $this->getAdjustmentNegative()) < .0001)) {
             return false;

app/code/Magento/Sales/i18n/en_US.csv

@@ -795,3 +795,5 @@ Created,Created
 "PDF Shipments","PDF Shipments"
 "PDF Creditmemos","PDF Creditmemos"
 Refunds,Refunds
+"Allow Zero GrandTotal for Creditmemo","Allow Zero GrandTotal for Creditmemo"
+"Allow Zero GrandTotal","Allow Zero GrandTotal"