Although it's not always reproducible, in some environments the attempt to access ezoe::browse ezjscore call will result in no content, in result of a failure to parse as json, an array that includes non properly encoded UFT8 characters.

In these environments, a variation of the patch certified in https://jira.ez.no/browse/EZP-19929, replacing the mb_convert_encoding with a utf8_encode seems to solve the issue perfectly.

Please certify if this patch will not break eZ's stability and functionality

--- extension/ezjscore/classes/ezjscajaxcontent.php
+++ extension/ezjscore/classes/ezjscajaxcontent.php
@@ -460,7 +460,7 @@
                             // json_encode/xmlEncode need UTF8 encoded strings
                             // (exif) metadata might not be for instance
                             // see https://jira.ez.no/browse/EZP-19929
-                            if ( !utf8_encode( $element ) )
+                            if ( !mb_check_encoding( $element, 'UTF-8' ) )
                             {
                                 $element = utf8_encode( $element );
                             }

steps to reproduce.

• Load an image with non utf8 content in exif fields into a site
• in an xml block field, attempt to select the image through a insert/edit object or image function
• IF you're affected with the encoding problem, the popup window will be blank