Get with closest_row_before on "hbase:meta" can return empty Cell during region merge/split. This gist reproduces the problem.

GetMetaRow.java

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.Admin;
import org.apache.hadoop.hbase.client.Get;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Table;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.HColumnDescriptor;

public class GetMetaRow {
	private static class Worker extends Thread {
		private Admin a;
		private TableName tn;
		public Worker(Admin admin, TableName tableName) {
			a = admin;
			tn = tableName;
		}
		@Override
		public void run() {
			while (true) {
				try {
					Thread.sleep(400);
					a.split(tn);
				} catch (InterruptedException e) {
					break;
				} catch (IOException e) {
					System.out.println("WTF");
				}
			}
		}
	}

	public static void main(String[] args) throws IOException, Exception {
		String table = "TestGetMetaRow";
		TableName tn = TableName.valueOf(table);
		Configuration hconfig = HBaseConfiguration.create();
		hconfig.set(HConstants.ZOOKEEPER_QUORUM, "localhost");
		Connection conn = ConnectionFactory.createConnection(hconfig);

		// create table
		Admin admin = conn.getAdmin();
		HTableDescriptor tableDescriptor = new HTableDescriptor(tn);
		tableDescriptor.addFamily(new HColumnDescriptor("cf"));
		admin.createTable(tableDescriptor);

		// populate it with keys
		Table t = conn.getTable(tn);
		for (int i = 0; i < 1000; i++) {
			byte[] data = Bytes.toBytes(String.format("%026d", i));
			Put put = new Put(data).addColumn("cf".getBytes(), null, data);
			t.put(put);
		}

		Worker w = new Worker(admin, tn);
        w.start();
		
		System.out.println("Starting gets on hbase:meta");
		// start getting the first row region of the table until the error
		Table tb = conn.getTable(TableName.valueOf("hbase:meta"));
		Get g = new Get(Bytes.toBytes(table + ",,:")).addFamily("info".getBytes()).setClosestRowBefore(true);
		while (true) {
			Result result = tb.get(g);
			if (Result.getTotalSizeOfCells(result) == 0) {
				System.out.println("GOT ZERO CELLS!!!!");
				break;
			}
		}

		w.interrupt();
		// clean up
		admin.disableTable(tn);
		admin.deleteTable(tn);
	}
}