Disconnection is not properly handled

[redtide]

On Android debug:

W System.err: java.io.IOException: bt socket closed, read return: -1
W System.err: 	at android.bluetooth.BluetoothSocket.read(BluetoothSocket.java:574)
W System.err: 	at android.bluetooth.BluetoothInputStream.read(BluetoothInputStream.java:96)
W System.err: 	at java.io.InputStream.read(InputStream.java:101)
W System.err: 	at org.qtproject.qt5.android.bluetooth.QtBluetoothInputStreamThread.run(QtBluetoothInputStreamThread.java:86)
W SmartHHC: QIODevice::write (QBluetoothSocket): device not open
W IInputConnectionWrapper: getExtractedText on inactive InputConnection
W IInputConnectionWrapper: getTextBeforeCursor on inactive InputConnection

Check various cases where a disconnection occurs and close the socket where needed.