Fix mem leak in idle threads

lib/MySQL_Thread.cpp

@@ -3252,7 +3252,8 @@ void MySQL_Threads_Handler::init(unsigned int num, size_t stack) {
 	assert(rc==0);
 	mysql_threads=(proxysql_mysql_thread_t *)calloc(num_threads,sizeof(proxysql_mysql_thread_t));
 #ifdef IDLE_THREADS
-	mysql_threads_idles=(proxysql_mysql_thread_t *)calloc(num_threads,sizeof(proxysql_mysql_thread_t));
+	if (GloVars.global.idle_threads)
+		mysql_threads_idles=(proxysql_mysql_thread_t *)calloc(num_threads,sizeof(proxysql_mysql_thread_t));
 #endif // IDLE_THREADS
 }
 
@@ -3264,9 +3265,11 @@ proxysql_mysql_thread_t * MySQL_Threads_Handler::create_thread(unsigned int tn,
 		}
 #ifdef IDLE_THREADS
 	} else {
-		if (pthread_create(&mysql_threads_idles[tn].thread_id, &attr, start_routine , &mysql_threads_idles[tn]) != 0) {
-			proxy_error("Thread creation\n");
-			assert(0);
+		if (GloVars.global.idle_threads) {
+			if (pthread_create(&mysql_threads_idles[tn].thread_id, &attr, start_routine , &mysql_threads_idles[tn]) != 0) {
+				proxy_error("Thread creation\n");
+				assert(0);
+			}
 		}
 #endif // IDLE_THREADS
 	}
@@ -5550,7 +5553,7 @@ SQLite3_result * MySQL_Threads_Handler::SQL3_Processlist() {
 			thr=(MySQL_Thread *)mysql_threads[i].worker;
 #ifdef IDLE_THREADS
 		} else {
-			if (mysql_thread___session_idle_show_processlist && mysql_threads_idles) {
+			if (GloVars.global.idle_threads && mysql_thread___session_idle_show_processlist && mysql_threads_idles) {
 				thr=(MySQL_Thread *)mysql_threads_idles[i-num_threads].worker;
 			}
 #endif // IDLE_THREADS