Set *name to NULL on failure.

lib/property_mosq.c

@@ -1064,7 +1064,10 @@ const mosquitto_property *mosquitto_property_read_string_pair(const mosquitto_pr
 	if(value){
 		*value = calloc(1, p->value.s.len+1);
 		if(!(*value)){
-			if(name) free(*name);
+			if(name){
+				free(*name);
+				*name = NULL;
+			}
 			return NULL;
 		}
 		memcpy(*value, p->value.s.v, p->value.s.len);