Fix startup without device

Startup without device causes a segmentation fault (at least here).
Show an error if the device_init is not successfull.

src/device.c

@@ -121,7 +121,7 @@ static gint query_program(const gint pgm_num)
 
 
 #define DEV_NAME_MAX_LEN 64
-void device_init(void)
+int device_init(void)
 {
 	guint dev_count;
 #ifdef HAVE_RTMIDI4
@@ -153,7 +153,7 @@ void device_init(void)
 	if (!found) {
 		g_critical("No MPKmini MK3 device found");
 		rtmidi_in_free(midi_in);
-		return;
+		return -1;
 	}
 	g_debug("Using device %d: %s", i, dev_name);
 	midi_out = rtmidi_out_create_default();
@@ -167,6 +167,8 @@ void device_init(void)
 
 	dev.in = midi_in;
 	dev.out = midi_out;
+
+	return 0;
 }
 
 

src/device.h

@@ -1,7 +1,7 @@
 #ifndef _DEVICE_H
 #define _DEVICE_H
 
-void device_init(void);
+int device_init(void);
 void device_close(void);
 gint device_read_pgm(gint pgm_num);
 gint device_write_pgm(gint pgm_num);

src/main.c

@@ -26,7 +26,10 @@ int main(int argc, char ** argv)
 	GtkWidget *app_win;
 
 	gtk_init(&argc, &argv);
-	device_init();
+	if (device_init() < 0) {
+		show_error();
+		return -1;
+	}
 	if (device_read_pgm(PGM_NUM_RAM) < 0) {
 		show_error();
 		return -1;