[AlterTable] Failed to alter table

[acelyc111]

Describe the bug
Add a column to a table, but the process blocked.
I found an exception on FE like:

2021-04-08 13:39:44,663 INFO (thrift-server-pool-613|804) [AlterHandler.handleFinishAlterTask():451] before handle alter task tablet 481265671, replica: [replicaId=481265672, BackendId=62134593, version=1, versionHash=0, dataSize=331285058, rowCount=1823157, lastFailedVersion=3, lastFailedVersionHash=6798223064512349591, lastSuccessVersion=27, lastSuccessVersionHash=5339720724553352740, lastFailedTimestamp=1617814890844, schemaHash=80261792, state=ALTER], task version: 3-6798223064512349591
2021-04-08 13:39:44,664 WARN (thrift-server-pool-613|804) [MasterImpl.finishTask():221] finish agent task error.
java.lang.IllegalStateException: 3
        at com.google.common.base.Preconditions.checkState(Preconditions.java:176) ~[jprotobuf-2.2.11-jar-with-dependencies.jar:?]
        at org.apache.doris.alter.AlterHandler.handleFinishAlterTask(AlterHandler.java:463) ~[palo-fe.jar:3.4.0]
        at org.apache.doris.master.MasterImpl.finishAlterTask(MasterImpl.java:847) ~[palo-fe.jar:3.4.0]
        at org.apache.doris.master.MasterImpl.finishTask(MasterImpl.java:210) [palo-fe.jar:3.4.0]
        at org.apache.doris.service.FrontendServiceImpl.finishTask(FrontendServiceImpl.java:376) [palo-fe.jar:3.4.0]
        at org.apache.doris.thrift.FrontendService$Processor$finishTask.getResult(FrontendService.java:1473) [palo-fe.jar:3.4.0]
        at org.apache.doris.thrift.FrontendService$Processor$finishTask.getResult(FrontendService.java:1458) [palo-fe.jar:3.4.0]
        at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:39) [libthrift-0.9.3.jar:0.9.3]
        at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:39) [libthrift-0.9.3.jar:0.9.3]
        at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:286) [libthrift-0.9.3.jar:0.9.3]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
        at java.lang.Thread.run(Thread.java:834) [?:?]

The new tablet's info can not be updated, and the process blocked.

Why we need this check in case 1?

if (replica.getVersion() > task.getVersion()) {
                // Case 2.2, do nothing
            } else {
                if (replica.getLastFailedVersion() > task.getVersion()) {
                    // Case 2.1
                    replica.updateVersionInfo(task.getVersion(), task.getVersionHash(), replica.getDataSize(), replica.getRowCount());
                    versionChanged = true;
                } else {
                    // Case 1
                    Preconditions.checkState(replica.getLastFailedVersion() == -1, replica.getLastFailedVersion());  // Why we need this check?
                    replica.updateVersionInfo(task.getVersion(), task.getVersionHash(), replica.getDataSize(), replica.getRowCount());
                    versionChanged = true;
                }
            }