message: Update FilterContext to convert BlendContext error to FilterContext error
diff: @@ -68,7 +68,10 @@ impl<'a> FilterContext<'a> {
  match (&self.next, &self.next2) {
  (None, None) => Err(FilterContextError::ValueNotFound.into()),
  (Some(fc), None) => fc.get_value(target),
  - (None, Some(bc)) => bc.get_value(target).map(Some),
  + (None, Some(bc)) => bc
  + .get_value(target)
  + .map(Some)
  + .map_err(|_| FilterContextError::ValueNotFound.into()),
  (Some(fc), Some(bc)) => match bc.get_value(target) {
  v @ Ok(_) => v.map(Some),
  Err(_) => fc.get_value(target),
  @@ -95,7 +98,10 @@ impl<'a> FilterContext<'a> {
  match (&self.next, &self.next2) {
  (None, None) => Err(FilterContextError::ValueNotFound.into()),
  (Some(fc), None) => fc.get_alias_value(table_alias, target),
  - (None, Some(bc)) => bc.get_alias_value(table_alias, target).map(Some),
  + (None, Some(bc)) => bc
  + .get_alias_value(table_alias, target)
  + .map(Some)
  + .map_err(|_| FilterContextError::ValueNotFound.into()),
  (Some(fc), Some(bc)) => match bc.get_alias_value(table_alias, target) {
  v @ Ok(_) => v.map(Some),
  Err(_) => fc.get_alias_value(table_alias, target),
  