Fix for metadata entries table for MOR tables containing Delete Files. (#1902)

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Closes #1884 

# Rationale for this change
table.inspect.entries() fails when table is MOR table and has Delete
Files present in it. Iceberg MOR Table is created via Apache Spark 3.5.0
with Iceberg 1.5.0 and it's being read via PyIceberg 0.9.0 using
StaticTable.from_metadata()


# Are these changes tested?
Yes

# Are there any user-facing changes?
No

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Author: guptaakashdeep

pyiceberg/table/inspect.py

@@ -205,9 +205,9 @@ def _readable_metrics_struct(bound_type: PrimitiveType) -> pa.StructType:
                             "record_count": entry.data_file.record_count,
                             "file_size_in_bytes": entry.data_file.file_size_in_bytes,
                             "column_sizes": dict(entry.data_file.column_sizes),
-                            "value_counts": dict(entry.data_file.value_counts),
-                            "null_value_counts": dict(entry.data_file.null_value_counts),
-                            "nan_value_counts": dict(entry.data_file.nan_value_counts),
+                            "value_counts": dict(entry.data_file.value_counts or {}),
+                            "null_value_counts": dict(entry.data_file.null_value_counts or {}),
+                            "nan_value_counts": dict(entry.data_file.nan_value_counts or {}),
                             "lower_bounds": entry.data_file.lower_bounds,
                             "upper_bounds": entry.data_file.upper_bounds,
                             "key_metadata": entry.data_file.key_metadata,