Fix NPE with FCP/ClientPut/IgnoreUSKDatehints

Regression by 524c45e327ec1553540d24583752c1278271d932 and 74c35d81b11ac34bbcc3c9b6b0f62a8d4cd6ad41

(freenet.support.PooledExecutor$MyThread, RequestStarter$SenderThread for freenet.client.async.TransientChosenBlock@225b7221(5585), ERROR): Caught java.lang.NullPointerException running job freenet.support.PooledExecutor$Job@358da448
java.lang.NullPointerException
        at freenet.client.async.USKInserter.insertSucceeded(USKInserter.java:167)
        at freenet.client.async.USKInserter.onSuccess(USKInserter.java:296)
        at freenet.client.async.SingleBlockInserter.onSuccess(SingleBlockInserter.java:461)
        at freenet.client.async.TransientChosenBlock.onInsertSuccess(TransientChosenBlock.java:48)
        at freenet.client.async.SingleBlockInserter$MySendableRequestSender.send(SingleBlockInserter.java:612)
        at freenet.client.async.ChosenBlock.send(ChosenBlock.java:70)
        at freenet.node.RequestStarter$SenderThread.run(RequestStarter.java:270)
        at freenet.support.PooledExecutor$MyThread.innerRun(PooledExecutor.java:247)
        at freenet.support.PooledExecutor$MyThread.realRun(PooledExecutor.java:187)
        at freenet.support.io.NativeThread.run(NativeThread.java:129)

Reported-by: TheSeeker@irc