EmbulkでConfigDefault("null")を指定して実行した時のエラー その2

embulk_run2.log

rm classpath/guava-jdk5-13.0.jar 後にrunを実行
$ embulk run ~/Desktop/gcs.yml
2015-02-27 05:37:45,892 +0900: Embulk v0.4.9
org/embulk/config/ModelManager.java:77:in `readObjectWithConfigSerDe': org.embulk.config.ConfigException: com.fasterxml.jackson.databind.JsonMappingException: Field 'last_path' is required but not set
 at [Source: N/A; line: -1, column: -1]
	from org/embulk/config/DataSourceImpl.java:198:in `loadConfig'
	from org/embulk/input/gcs/GcsFileInputPlugin.java:98:in `transaction'
	from org/embulk/spi/FileInputRunner.java:60:in `transaction'
	from org/embulk/exec/LocalExecutor.java:431:in `doRun'
	from org/embulk/exec/LocalExecutor.java:40:in `access$000'
	from org/embulk/exec/LocalExecutor.java:359:in `run'
	from org/embulk/exec/LocalExecutor.java:355:in `run'
	from org/embulk/spi/Exec.java:21:in `doWith'
	from org/embulk/exec/LocalExecutor.java:355:in `run'
	from org/embulk/command/Runner.java:119:in `run'
	from org/embulk/command/Runner.java:72:in `main'
	from java/lang/reflect/Method.java:483:in `invoke'
	from file:/Users/satoshi/.embulk/bin/embulk!/embulk/command/embulk_run.rb:295:in `run'
	from classpath:embulk/command/embulk.rb:43:in `(root)'
	from classpath_3a_embulk/command/classpath:embulk/command/embulk.rb:43:in `(root)'
	from org/embulk/cli/Main.java:13:in `main'
Caused by:
TaskSerDe.java:177:in `deserialize': com.fasterxml.jackson.databind.JsonMappingException: Field 'last_path' is required but not set
 at [Source: N/A; line: -1, column: -1]
	from ObjectMapper.java:3532:in `_readValue'
	from ObjectMapper.java:1868:in `readValue'
	from ModelManager.java:74:in `readObjectWithConfigSerDe'
	from DataSourceImpl.java:198:in `loadConfig'
	from GcsFileInputPlugin.java:98:in `transaction'
	from FileInputRunner.java:60:in `transaction'
	from LocalExecutor.java:431:in `doRun'
	from LocalExecutor.java:40:in `access$000'
	from LocalExecutor.java:359:in `run'
	from LocalExecutor.java:355:in `run'
	from Exec.java:21:in `doWith'
	from LocalExecutor.java:355:in `run'
	from Runner.java:119:in `run'
	from Runner.java:72:in `main'
	from NativeMethodAccessorImpl.java:-2:in `invoke0'
	from NativeMethodAccessorImpl.java:62:in `invoke'
	from DelegatingMethodAccessorImpl.java:43:in `invoke'
	from Method.java:483:in `invoke'
	from JavaMethod.java:470:in `invokeDirectWithExceptionHandling'
	from JavaMethod.java:328:in `invokeDirect'
	from InstanceMethodInvoker.java:71:in `call'
	from CachingCallSite.java:346:in `cacheAndCall'
	from CachingCallSite.java:204:in `call'
	from CallTwoArgNode.java:59:in `interpret'
	from NewlineNode.java:105:in `interpret'
	from BlockNode.java:71:in `interpret'
	from CaseNode.java:138:in `interpret'
	from NewlineNode.java:105:in `interpret'
	from BlockNode.java:71:in `interpret'
	from ASTInterpreter.java:74:in `INTERPRET_METHOD'
	from InterpretedMethod.java:182:in `call'
	from DefaultMethod.java:203:in `call'
	from CachingCallSite.java:326:in `cacheAndCall'
	from CachingCallSite.java:170:in `call'
	from classpath:embulk/command/embulk.rb:43:in `__file__'
	from classpath:embulk/command/embulk.rb:-1:in `load'
	from Ruby.java:866:in `runScript'
	from Ruby.java:859:in `runScript'
	from Ruby.java:728:in `runNormally'
	from Ruby.java:577:in `runFromMain'
	from Main.java:395:in `doRunFromMain'
	from Main.java:290:in `internalRun'
	from Main.java:217:in `run'
	from Main.java:197:in `main'
	from Main.java:13:in `main'