Fix documentation omission around mosquitto_reinitialise.

Closes #2489. Thanks to rroguski

ChangeLog.txt

@@ -27,6 +27,7 @@ Client library:
 - Fix incorrect use of SSL_connect. Closes #2594.
 - Don't set SIGPIPE to ignore, use MSG_NOSIGNAL instead. Closes #2564.
 - Add documentation of struct mosquitto_message to header. Closes #2561.
+- Fix documentation omission around mosquitto_reinitialise. Closes #2489.
 
 Clients:
 - Fix mosquitto_pub incorrectly reusing topic aliases when reconnecting.

include/mosquitto.h

@@ -349,6 +349,7 @@ libmosq_EXPORT void mosquitto_destroy(struct mosquitto *mosq);
  * 	MOSQ_ERR_SUCCESS -        on success.
  * 	MOSQ_ERR_INVAL -          if the input parameters were invalid.
  * 	MOSQ_ERR_NOMEM -          if an out of memory condition occurred.
+ * 	MOSQ_ERR_MALFORMED_UTF8 - if the client id is not valid UTF-8.
  *
  * See Also:
  * 	<mosquitto_new>, <mosquitto_destroy>

lib/mosquitto.c

@@ -163,6 +163,9 @@ int mosquitto_reinitialise(struct mosquitto *mosq, const char *id, bool clean_st
 			return MOSQ_ERR_MALFORMED_UTF8;
 		}
 		mosq->id = mosquitto__strdup(id);
+		if(!mosq->id){
+			return MOSQ_ERR_NOMEM;
+		}
 	}
 	mosq->in_packet.payload = NULL;
 	packet__cleanup(&mosq->in_packet);