Increase thread stack size.

src/buttons.c

@@ -29,7 +29,7 @@ static void button_Process(virtual_timer_t *vtp, void *p) {
 /*
  * BTN serving thread.
  */
-static THD_WORKING_AREA(waBTNThread, 128);
+static THD_WORKING_AREA(waBTNThread, 256);
 static THD_FUNCTION(BTNThread, arg) {
   (void)arg;
   static int pause = 0;