Don't re-initialize my_audio if espeak_ng_InitializeOutput is called multiple times.

src/libespeak-ng/speech.c

 	out_samplerate = 0;
 
 #ifdef HAVE_PCAUDIOLIB_AUDIO_H
-	my_audio = create_audio_device_object(device, "eSpeak", "Text-to-Speech");
+	if (my_audio == NULL)
+		my_audio = create_audio_device_object(device, "eSpeak", "Text-to-Speech");
 #endif
 
 	// buffer_length is in mS, allocate 2 bytes per sample
 #ifdef HAVE_PCAUDIOLIB_AUDIO_H
 		audio_object_close(my_audio);
 		audio_object_destroy(my_audio);
+		my_audio = NULL;
 #endif
 		out_samplerate = 0;
 	}