fix: revert file_append empty-contents validation broken by integration test

Signed-off-by: Mounil Kanakhara <mounilkankhara@gmail.com>

Author: Mounil2005

src/hiero_sdk_python/file/file_append_transaction.py

@@ -168,12 +168,13 @@ def _build_proto_body(self) -> file_append_pb2.FileAppendTransactionBody:
         # Calculate the current chunk's content
         if self.file_id is None:
             raise ValueError("Missing required FileID")
-        if not self.contents:
-            raise ValueError("Missing required file contents")
 
-        start_index = self._current_chunk_index * self.chunk_size
-        end_index = min(start_index + self.chunk_size, len(self.contents))
-        chunk_contents = self.contents[start_index:end_index]
+        if self.contents is None:
+            chunk_contents = b""
+        else:
+            start_index = self._current_chunk_index * self.chunk_size
+            end_index = min(start_index + self.chunk_size, len(self.contents))
+            chunk_contents = self.contents[start_index:end_index]
 
         return file_append_pb2.FileAppendTransactionBody(
             fileID=self.file_id._to_proto() if self.file_id else None, contents=chunk_contents

tests/unit/file_append_transaction_test.py

@@ -159,17 +159,6 @@ def test_build_transaction_body_missing_file_id():
         file_tx.build_transaction_body()
 
 
-def test_build_proto_body_raises_on_empty_contents():
-    """Test _build_proto_body raises when contents is None or empty."""
-    file_id = FileId(0, 0, 99)
-
-    with pytest.raises(ValueError, match="Missing required file contents"):
-        FileAppendTransaction(file_id=file_id)._build_proto_body()
-
-    with pytest.raises(ValueError, match="Missing required file contents"):
-        FileAppendTransaction(file_id=file_id, contents=b"")._build_proto_body()
-
-
 def test_build_scheduled_body():
     """Test building a schedulable file append transaction body."""
     file_id = FileId(0, 0, 12345)