Adjusted fix for issue in CryptoFileSystem when deleting a file

* CryptoWritableFile now only invokes writeTaks.get if not already
closed
* CryptoWritableFile now cancels writeTask before delete

main/filesystem-crypto/src/main/java/org/cryptomator/filesystem/crypto/CiphertextWriter.java

@@ -1,5 +1,7 @@
 package org.cryptomator.filesystem.crypto;
 
+import java.io.InterruptedIOException;
+import java.io.UncheckedIOException;
 import java.nio.ByteBuffer;
 import java.util.concurrent.Callable;
 
@@ -25,7 +27,7 @@ class CiphertextWriter implements Callable<Void> {
 				file.write(ciphertext);
 			}
 		} catch (InterruptedException e) {
-			Thread.currentThread().interrupt();
+			throw new UncheckedIOException(new InterruptedIOException("Task interrupted while waiting for ciphertext"));
 		}
 		return null;
 	}

main/filesystem-crypto/src/main/java/org/cryptomator/filesystem/crypto/CryptoWritableFile.java

@@ -23,9 +23,13 @@ import org.cryptomator.crypto.engine.FileContentCryptor;
 import org.cryptomator.crypto.engine.FileContentEncryptor;
 import org.cryptomator.filesystem.WritableFile;
 import org.cryptomator.io.ByteBuffers;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 class CryptoWritableFile implements WritableFile {
 
+	private static final Logger LOG = LoggerFactory.getLogger(CryptoWritableFile.class);
+
 	final WritableFile file;
 	private final ExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
 	private final FileContentEncryptor encryptor;
@@ -82,6 +86,7 @@ class CryptoWritableFile implements WritableFile {
 
 	@Override
 	public void delete() {
+		writeTask.cancel(true);
 		file.delete();
 	}
 
@@ -107,9 +112,9 @@ class CryptoWritableFile implements WritableFile {
 	@Override
 	public void close() {
 		try {
-			encryptor.append(FileContentCryptor.EOF);
-			writeTask.get();
 			if (file.isOpen()) {
+				encryptor.append(FileContentCryptor.EOF);
+				writeTask.get();
 				writeHeader();
 				// TODO append padding
 			}

main/filesystem-inmemory/src/main/java/org/cryptomator/filesystem/inmem/InMemoryWritableFile.java

@@ -27,7 +27,7 @@ public class InMemoryWritableFile implements WritableFile {
 	private final Consumer<Void> deleter;
 	private final WriteLock writeLock;
 
-	private boolean open;
+	private boolean open = true;
 	private int position = 0;
 
 	public InMemoryWritableFile(Consumer<Instant> lastModifiedSetter, Consumer<Instant> creationTimeSetter, Supplier<ByteBuffer> contentGetter, Consumer<ByteBuffer> contentSetter, Consumer<Void> deleter,