added check for null pointer before fixing tokens after parsing is done

jsmn.c

@@ -289,10 +289,12 @@ int jsmn_parse(jsmn_parser *parser, const char *js, size_t len,
 		}
 	}
 
-	for (i = parser->toknext - 1; i >= 0; i--) {
-		/* Unmatched opened object or array */
-		if (tokens[i].start != -1 && tokens[i].end == -1) {
-			return JSMN_ERROR_PART;
+	if (tokens != NULL) {
+		for (i = parser->toknext - 1; i >= 0; i--) {
+			/* Unmatched opened object or array */
+			if (tokens[i].start != -1 && tokens[i].end == -1) {
+				return JSMN_ERROR_PART;
+			}
 		}
 	}