Resolved undefined index issue for import adapter

Author: jaimin-ktpl

app/code/Magento/ImportExport/Model/Import/Entity/AbstractEntity.php

@@ -408,7 +408,9 @@ protected function _saveValidatedBunches()
             if ($source->valid()) {
                 try {
                     $rowData = $source->current();
-                    $skuSet[$rowData['sku']] = true;
+                    if (array_key_exists('sku', $rowData)) {
+                        $skuSet[$rowData['sku']] = true;
+                    }
                 } catch (\InvalidArgumentException $e) {
                     $this->addRowError($e->getMessage(), $this->_processedRowsCount);
                     $this->_processedRowsCount++;