Fix assertion 'bytes_copied > 0' in JSON.stringify()

JerryScript-DCO-1.0-Signed-off-by: Roland Takacs rtakacs.u-szeged@partner.samsung.com

jerry-core/ecma/builtin-objects/ecma-builtin-json.cpp

@@ -1129,7 +1129,7 @@ ecma_builtin_json_quote (ecma_string_t *string_p) /**< string that should be quo
   ssize_t bytes_copied = ecma_string_to_utf8_string (string_p,
                                                      zt_string_buff,
                                                      (ssize_t) string_buf_size);
-  JERRY_ASSERT (bytes_copied > 0);
+  JERRY_ASSERT (bytes_copied > 0 || !string_len);
 
   /* 2. */
   for (ecma_length_t i = 0; i < string_len; i++)

tests/jerry/json-stringify.js

@@ -14,6 +14,8 @@
 // limitations under the License.
 
 // Checking quoting strings
+assert (JSON.stringify ("") === '""');
+
 normal_string = "asdasd";
 assert (JSON.stringify (normal_string) == '"asdasd"');