Fix bug for Index clear_history (#522)

We always need to have `0` as the first ingestion timestamp, even if we don't have respective write fragments in the base index arrays. If not, `updates` that are before the `first_ingestion_timestamp` will not be visible.

Author: NikolaosPapailiou

apis/python/src/tiledb/vector_search/index.py

@@ -638,7 +638,7 @@ def clear_history(
             new_partition_history = []
             i = 0
             for ingestion_timestamp in ingestion_timestamps:
-                if ingestion_timestamp > timestamp:
+                if ingestion_timestamp == 0 or ingestion_timestamp > timestamp:
                     new_ingestion_timestamps.append(ingestion_timestamp)
                     new_base_sizes.append(base_sizes[i])
                     new_partition_history.append(partition_history[i])