Forward port of magento-partners/magento2ce#63 from 2.1 to 2.3

Author: WilXP

app/code/Magento/ImportExport/Model/ResourceModel/Import/Data.php

@@ -159,9 +159,17 @@ public function getNextBunch()
      */
     public function saveBunch($entity, $behavior, array $data)
     {
+        $encodedData = $this->jsonHelper->jsonEncode($data);
+
+        if (json_last_error()!==JSON_ERROR_NONE && empty($encodedData)) {
+            throw new \Magento\Framework\Exception\ValidatorException(
+                __('Error in CSV: ' . json_last_error_msg())
+            );
+        }
+
         return $this->getConnection()->insert(
             $this->getMainTable(),
-            ['behavior' => $behavior, 'entity' => $entity, 'data' => $this->jsonHelper->jsonEncode($data)]
+            ['behavior' => $behavior, 'entity' => $entity, 'data' => $encodedData]
         );
     }
 }