When cancelling indexinb background tasks, no exceptions should be shown

[koppor]

I canceled the background tasks (a window was popping up). I get some wired output.

<============-> 92% EXECUTING [4m 16s]
> :run
23:42:01.993 [pool-3-thread-1] WARN  org.jabref.gui.LibraryTab - Could not add the document to the index!
java.nio.channels.ClosedByInterruptException: null
        at java.nio.channels.spi.AbstractInterruptibleChannel.end(AbstractInterruptibleChannel.java:199) ~[?:?]
        at sun.nio.ch.FileChannelImpl.endBlocking(FileChannelImpl.java:168) ~[?:?]
        at sun.nio.ch.FileChannelImpl.size(FileChannelImpl.java:392) ~[?:?]
        at org.apache.lucene.store.NIOFSDirectory$NIOFSIndexInput.<init>(NIOFSDirectory.java:118) ~[lucene.jar:?]
        at org.apache.lucene.store.NIOFSDirectory.openInput(NIOFSDirectory.java:86) ~[lucene.jar:?]
        at org.apache.lucene.store.Directory.openChecksumInput(Directory.java:157) ~[lucene.jar:?]
        at org.apache.lucene.index.SegmentInfos.readCommit(SegmentInfos.java:289) ~[lucene.jar:?]
        at org.apache.lucene.index.StandardDirectoryReader$1.doBody(StandardDirectoryReader.java:64) ~[lucene.jar:?]
        at org.apache.lucene.index.StandardDirectoryReader$1.doBody(StandardDirectoryReader.java:61) ~[lucene.jar:?]
        at org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(SegmentInfos.java:720) ~[lucene.jar:?]
        at org.apache.lucene.index.StandardDirectoryReader.open(StandardDirectoryReader.java:84) ~[lucene.jar:?]
        at org.apache.lucene.index.DirectoryReader.open(DirectoryReader.java:64) ~[lucene.jar:?]
        at org.jabref.logic.pdf.search.indexing.PdfIndexer.writeToIndex(PdfIndexer.java:193) ~[JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.PdfIndexer.addToIndex(PdfIndexer.java:109) ~[JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.IndexingTaskManager.lambda$addToIndex$3(IndexingTaskManager.java:79) ~[JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.IndexingTaskManager.call(IndexingTaskManager.java:43) [JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.IndexingTaskManager.call(IndexingTaskManager.java:18) [JabRef-100.0.0.jar:?]
        at org.jabref.gui.util.DefaultTaskExecutor$1.call(DefaultTaskExecutor.java:160) [JabRef-100.0.0.jar:?]
        at javafx.concurrent.Task$TaskCallable.call(Task.java:1425) [javafx.graphics:?]
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?]
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) [?:?]
        at java.lang.Thread.run(Thread.java:831) [?:?]
<============-> 92% EXECUTING [4m 16s]
23:42:02.360 [pool-3-thread-1] WARN  org.jabref.gui.LibraryTab - Could not add the document to the index!
java.nio.channels.ClosedByInterruptException: null
        at java.nio.channels.spi.AbstractInterruptibleChannel.end(AbstractInterruptibleChannel.java:199) ~[?:?]
        at sun.nio.ch.FileChannelImpl.endBlocking(FileChannelImpl.java:168) ~[?:?]
        at sun.nio.ch.FileChannelImpl.size(FileChannelImpl.java:392) ~[?:?]
        at org.apache.lucene.store.NIOFSDirectory$NIOFSIndexInput.<init>(NIOFSDirectory.java:118) ~[lucene.jar:?]
        at org.apache.lucene.store.NIOFSDirectory.openInput(NIOFSDirectory.java:86) ~[lucene.jar:?]
        at org.apache.lucene.store.Directory.openChecksumInput(Directory.java:157) ~[lucene.jar:?]
        at org.apache.lucene.index.SegmentInfos.readCommit(SegmentInfos.java:289) ~[lucene.jar:?]
        at org.apache.lucene.index.StandardDirectoryReader$1.doBody(StandardDirectoryReader.java:64) ~[lucene.jar:?]
        at org.apache.lucene.index.StandardDirectoryReader$1.doBody(StandardDirectoryReader.java:61) ~[lucene.jar:?]
        at org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(SegmentInfos.java:720) ~[lucene.jar:?]
        at org.apache.lucene.index.StandardDirectoryReader.open(StandardDirectoryReader.java:84) ~[lucene.jar:?]
        at org.apache.lucene.index.DirectoryReader.open(DirectoryReader.java:64) ~[lucene.jar:?]
        at org.jabref.logic.pdf.search.indexing.PdfIndexer.writeToIndex(PdfIndexer.java:193) ~[JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.PdfIndexer.addToIndex(PdfIndexer.java:109) ~[JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.IndexingTaskManager.lambda$addToIndex$3(IndexingTaskManager.java:79) ~[JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.IndexingTaskManager.call(IndexingTaskManager.java:43) [JabRef-100.0.0.jar:?]
        at org.jabref.logic.pdf.search.indexing.IndexingTaskManager.call(IndexingTaskManager.java:18) [JabRef-100.0.0.jar:?]
        at org.jabref.gui.util.DefaultTaskExecutor$1.call(DefaultTaskExecutor.java:160) [JabRef-100.0.0.jar:?]
        at javafx.concurrent.Task$TaskCallable.call(Task.java:1425) [javafx.graphics:?]
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?]
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) [?:?]
        at java.lang.Thread.run(Thread.java:831) [?:?]