Moodle 2.7 russian translation filter issue

[vazotov]

Hello!

I've found out an issue on my moodle 2.7 with russian translation. All filters don't work in assign tabs (e.g. in assisgning course into program) because of encoding problems.
In local/elisprogram/lib/deepsight/lib/filters/date.filter.php file in get_js_opts() method line
$opts['lang_days'][$i] = $opts['lang_days'][$i]{0};
returns incorrect substring and cause js error which leads to filter doesn't show.