fix: if new_partitions is size 0, do not enforce size check (#1673)

Do not enforce new_partitions and change_stream_continuation_tokens to be the same size if new_partitions has size of 0 because Cloud Bigtable backend may not be updated to serve new_partitions field yet.

`new_partitions` is a new field and the backend may not be serving this field.

Change-Id: Id21c293b92c304f05b905ca8e8b3988b9241866e

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Fixes #<issue_number_goes_here> ☕️

If you write sample code, please follow the [samples format](
https://togithub.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/models/CloseStream.java

@@ -48,7 +48,8 @@ private static CloseStream create(
           !changeStreamContinuationTokens.isEmpty(),
           "A non-OK CloseStream should have continuation token(s).");
       Preconditions.checkState(
-          changeStreamContinuationTokens.size() == newPartitions.size(),
+          newPartitions.size() == 0
+              || changeStreamContinuationTokens.size() == newPartitions.size(),
           "Number of continuation tokens does not match number of new partitions.");
     }
     return new AutoValue_CloseStream(

google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/models/ChangeStreamRecordTest.java

@@ -236,9 +236,45 @@ public void closeStreamTokenAndNewPartitionCountMismatchedTest() {
                 StreamContinuationToken.newBuilder()
                     .setPartition(StreamPartition.newBuilder().setRowRange(rowRange))
                     .setToken(token))
+            .addNewPartitions(StreamPartition.newBuilder().setRowRange(rowRange))
+            .addNewPartitions(StreamPartition.newBuilder().setRowRange(rowRange))
             .setStatus(status)
             .build();
     Assert.assertThrows(
         IllegalStateException.class, (ThrowingRunnable) CloseStream.fromProto(closeStreamProto));
   }
+
+  // Tests that number of continuation tokens and new partitions don't need to match if new
+  // partitions is empty.
+  @Test
+  public void closeStreamTokenAndZeroNewPartitionMismatchNoExceptionTest()
+      throws IOException, ClassNotFoundException {
+    Status status = Status.newBuilder().setCode(11).build();
+    RowRange rowRange =
+        RowRange.newBuilder()
+            .setStartKeyClosed(ByteString.copyFromUtf8(""))
+            .setEndKeyOpen(ByteString.copyFromUtf8("apple"))
+            .build();
+    String token = "close-stream-token-1";
+    ReadChangeStreamResponse.CloseStream closeStreamProto =
+        ReadChangeStreamResponse.CloseStream.newBuilder()
+            .addContinuationTokens(
+                StreamContinuationToken.newBuilder()
+                    .setPartition(StreamPartition.newBuilder().setRowRange(rowRange))
+                    .setToken(token))
+            .setStatus(status)
+            .build();
+    CloseStream closeStream = CloseStream.fromProto(closeStreamProto);
+
+    ByteArrayOutputStream bos = new ByteArrayOutputStream();
+    ObjectOutputStream oos = new ObjectOutputStream(bos);
+    oos.writeObject(closeStream);
+    oos.close();
+    ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()));
+    CloseStream actual = (CloseStream) ois.readObject();
+    assertThat(actual.getChangeStreamContinuationTokens())
+        .isEqualTo(closeStream.getChangeStreamContinuationTokens());
+    assertThat(actual.getStatus()).isEqualTo(closeStream.getStatus());
+    assertThat(actual.getNewPartitions()).isEqualTo(closeStream.getNewPartitions());
+  }
 }