Initialise sockpairR/W to invalid in `mosquitto_reinitialise()`

This avoids closing invalid sockets in `mosquitto_destroy()` on error.

Closes #2326. Thanks to Arrigo Zanette.

ChangeLog.txt

@@ -8,6 +8,10 @@ Broker:
 - Various fixes around inflight quota management. Closes #2306.
 - Fix problem parsing config files with Windows line endings. Closes #2297.
 
+Client library:
+- Initialise sockpairR/W to invalid in `mosquitto_reinitialise()` to avoid
+  closing invalid sockets in `mosquitto_destroy()` on error. Closes #2326.
+
 
 2.0.12 - 2021-08-31
 ===================

lib/mosquitto.c

@@ -155,6 +155,8 @@ int mosquitto_reinitialise(struct mosquitto *mosq, const char *id, bool clean_st
 	}
 	mosq->protocol = mosq_p_mqtt311;
 	mosq->sock = INVALID_SOCKET;
+	mosq->sockpairR = INVALID_SOCKET;
+	mosq->sockpairW = INVALID_SOCKET;
 	mosq->keepalive = 60;
 	mosq->clean_start = clean_start;
 	if(id){