PIT:GIFWriter.endWriteSequence() does not throw Excpn when prepareWriteSeq() is not called

According to the API spec of ImageWriter.endWriteSequence(), this method is supposed to throw an IllegalStateException when prepareWriteSequence() is not called prior to this. I am just creating a writer and calling this method directly. This method does not throw an IllegalStateException.

This is reproducible on all platforms with the following PIT build:
java version "1.6.0-2d.pit-jcg-win-03"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-2d.pit-jcg-win-03-java2d_23_may_2005_02_25-b00)
Java HotSpot(TM) Client VM (build 1.6.0-ea-b37, mixed mode)

I have attached a sample test. Execute the sample test. If you dont see any IllegalStateException on the console, the bug is reproduced.
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