fifo, event: fix thread management

src/libespeak-ng/event.c

 static bool my_terminate_is_required = 0;
 // my_thread: polls the audio duration and compares it to the duration of the first event.
 static pthread_t my_thread;
-static bool thread_inited;
+static bool thread_inited = false;
 
 static t_espeak_callback *my_callback = NULL;
 static bool my_event_is_running = false;

src/libespeak-ng/fifo.c

 static t_espeak_command *pop(void);
 static void init(int process_parameters);
 static int node_counter = 0;
+static bool thread_inited = false;
 
 enum {
 	MAX_NODE_COUNTER = 400,
 	                      (void *)NULL)) {
 		assert(0);
 	}
+	thread_inited = true;
 
 	pthread_attr_destroy(&a_attrib);
 
 espeak_ng_STATUS fifo_add_commands(t_espeak_command *command1, t_espeak_command *command2)
 {
 	espeak_ng_STATUS status;
+	if (!thread_inited) {
+		return ENS_NOT_INITIALIZED;
+	}
 	if ((status = pthread_mutex_lock(&my_mutex)) != ENS_OK)
 		return status;
 
 
 espeak_ng_STATUS fifo_stop()
 {
+	if (!thread_inited) return ENS_OK;
 	espeak_ng_STATUS status;
 	if ((status = pthread_mutex_lock(&my_mutex)) != ENS_OK)
 		return status;
 
 int fifo_is_busy()
 {
-	return my_command_is_running;
+	if (!thread_inited) return false;
+	pthread_mutex_lock(&my_mutex);
+	bool running = my_command_is_running;
+	pthread_mutex_unlock(&my_mutex);
+	return running;
 }
 
 static int sleep_until_start_request_or_inactivity()
 
 void fifo_terminate()
 {
+	if (!thread_inited) return;
+
 	pthread_mutex_lock(&my_mutex);
 	my_terminate_is_required = true;
 	pthread_mutex_unlock(&my_mutex);
 	pthread_cond_signal(&my_cond_start_is_required);
 	pthread_join(my_thread, NULL);
 	my_terminate_is_required = false;
+	thread_inited = false;
 
 	pthread_mutex_destroy(&my_mutex);
 	pthread_cond_destroy(&my_cond_start_is_required);

src/libespeak-ng/speech.c

 		my_audio = create_audio_device_object(device, "eSpeak", "Text-to-Speech");
 #endif
 
+#if USE_ASYNC
+	if ((my_mode & ENOUTPUT_MODE_SYNCHRONOUS) == 0) fifo_init();
+#endif
 
 	// Don't allow buffer be smaller than safe minimum
 	if (buffer_length < min_buffer_length)
 	SetParameter(espeakPUNCTUATION, option_punctuation, 0);
 	SetParameter(espeakWORDGAP, 0, 0);
 
-#if USE_ASYNC
-	fifo_init();
-#endif
-
 	option_phonemes = 0;
 	option_phoneme_events = 0;