interpret empty to_encoding as encoding not set what results in current_internal_encoding

diff --git a/ext/mbstring/mbstring.c b/ext/mbstring/mbstring.c
index cfd3bfdf657bde282ce8d3919f9da4a6d9fab354..63394d7bdcd28c5aee3a2e8a6ca63b0032dbdc9d 100644 (file)
--- a/ext/mbstring/mbstring.c
+++ b/ext/mbstring/mbstring.c
@@ -2070,7 +2070,7 @@ PHPAPI char * php_mb_convert_encoding(char *input, size_t length, char *_to_enco
                return NULL;
        }
        /* new encoding */
-       if (_to_encoding) {
+       if (_to_encoding && strlen(_to_encoding)) {
                to_encoding = mbfl_name2no_encoding(_to_encoding);
                if (to_encoding == mbfl_no_encoding_invalid) {
                        php_error(E_WARNING, "%s() unknown encoding \"%s\"",