message: add default for u64 source
diff: @@ -21,11 +21,11 @@ impl Queryable for U64CounterSource {
  impl<T> Producer<T> for U64CounterSource
  where
  - T: FromPrimitive + TypeInfo,
  + T: FromPrimitive + TypeInfo + Default,
  {
  fn produce(&mut self) -> Result<T> {
  let ret = self.counter;
  self.counter += 1;
  - Ok(FromPrimitive::from_u64(ret).unwrap())
  + Ok(FromPrimitive::from_u64(ret).unwrap_or_default())
  }
  }
  