refactor(cdk): fix emit_slice logic - default True when parent_record exists, False on KeyError

- emit_slice = parent_record is not None (default True when we have a record)
- Set emit_slice = False only when KeyError occurs during dpath.get
- This makes the logic clearer: we want to emit slices by default, skip only on error

Co-Authored-By: Daryna Ishchenko <darina.ishchenko17@gmail.com>

Author: devin-ai-integration[bot]

airbyte_cdk/sources/declarative/partition_routers/substream_partition_router.py

@@ -212,7 +212,7 @@ def stream_slices(self) -> Iterable[StreamSlice]:
                     for parent_record, is_last_record_in_slice in iterate_with_last_flag(
                         partition.read()
                     ):
-                        emit_slice = False
+                        emit_slice = parent_record is not None
                         if parent_record is not None:
                             # In the previous CDK implementation, state management was done internally by the stream.
                             # However, this could cause issues when doing availability check for example as the availability
@@ -234,10 +234,9 @@ def stream_slices(self) -> Iterable[StreamSlice]:
                                     record_data,  # type: ignore [arg-type]
                                     parent_field,
                                 )
-                                emit_slice = True
                             except KeyError:
                                 # FIXME a log here would go a long way for debugging
-                                pass
+                                emit_slice = False
 
                             if emit_slice:
                                 # Add extra fields