MAGETWO-38417: Table Rates shipping method does not work

- Add type checking

Author: Viktor Tymchynskyi

lib/internal/Magento/Framework/Filesystem/Driver/File.php

@@ -645,12 +645,16 @@ public function fileWrite($resource, $data)
     public function filePutCsv($resource, array $data, $delimiter = ',', $enclosure = '"')
     {
         /**
-        * Security enhancement for CSV data processing by Excel-like applications.
-        * @see https://bugzilla.mozilla.org/show_bug.cgi?id=1054702
-        */
+         * Security enhancement for CSV data processing by Excel-like applications.
+         * @see https://bugzilla.mozilla.org/show_bug.cgi?id=1054702
+         *
+         * @var $value string|\Magento\Framework\Phrase
+         */
         foreach ($data as $key => $value) {
-            /** @var $value string|\Magento\Framework\Phrase */
-            $value = (string)$value;
+
+            if (!is_string($value)) {
+                $value = (string)$value;
+            }
             if (isset($value[0]) && $value[0] === '=') {
                 $data[$key] = ' ' . $value;
             }

lib/internal/Magento/Framework/Filesystem/Io/File.php

@@ -180,10 +180,13 @@ public function streamWriteCsv(array $row, $delimiter = ',', $enclosure = '"')
         /**
          * Security enhancement for CSV data processing by Excel-like applications.
          * @see https://bugzilla.mozilla.org/show_bug.cgi?id=1054702
+         *
+         * @var $value string|\Magento\Framework\Phrase
          */
         foreach ($row as $key => $value) {
-            /** @var $value string|\Magento\Framework\Phrase */
-            $value = (string)$value;
+            if (!is_string($value)) {
+                $value = (string)$value;
+            }
             if (isset($value[0]) && $value[0] === '=') {
                 $row[$key] = ' ' . $value;
             }