fixed crash of Formatter when intl is not installed

framework/i18n/Formatter.php

@@ -8,7 +8,6 @@
 namespace yii\i18n;
 
 use DateTime;
-use DateTimeInterface;
 use IntlDateFormatter;
 use NumberFormatter;
 use Yii;
@@ -1010,7 +1009,9 @@ class Formatter extends Component
         // disable grouping for edge cases like 1023 to get 1023 B instead of 1,023 B
         $oldThousandSeparator = $this->thousandSeparator;
         $this->thousandSeparator = '';
+        if ($this->_intlLoaded) {
             $options[NumberFormatter::GROUPING_USED] = false;
+        }
         // format the size value
         $params = [
             // this is the unformatted number used for the plural rule