MDEV-23941: strings/json_lib.c:893:12: style: Suspicious condition

The characters parsed are always ascii characters, hence one byte. This means that the code did not have "incorrect" logic because the boolean condition, if true, would also evaluate to the value of 1. The condition however is semantically wrong, assuming a length is equal to the condition outcome. Change paranthesis to make it also read according to the intent.

Author: cvicentiu

strings/json_lib.c

@@ -890,7 +890,7 @@ int json_read_keyname_chr(json_engine_t *j)
  case S_QUOTE:
  for (;;) /* Skip spaces until ':'. */
  {
- if ((c_len= json_next_char(&j->s) > 0))
+ if ((c_len= json_next_char(&j->s)) > 0)
  {
  if (j->s.c_next == ':')
  {