Handle serial port errors

[xlfe]

Eg - serial port is unplugged

Exception in thread "/dev/tty.wchusbserial1410" java.io.IOException: read() < 0 , errno()=6
	at purejavacomm.PureJavaSerialPort$2.read(PureJavaSerialPort.java:922)
	at purejavacomm.PureJavaSerialPort$2.read(PureJavaSerialPort.java:729)
	at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at clojure.lang.Reflector.invokeMatchingMethod(Reflector.java:93)
	at clojure.lang.Reflector.invokeNoArgInstanceMember(Reflector.java:313)
	at jonure.core$make_handler$fn__18179.invoke(core.clj:15)
	at serial.core$listen_BANG_$reify__14056.serialEvent(core.clj:139)
	at purejavacomm.PureJavaSerialPort.sendDataEvents(PureJavaSerialPort.java:92)
	at purejavacomm.PureJavaSerialPort.access$2400(PureJavaSerialPort.java:43)
	at purejavacomm.PureJavaSerialPort$3.run(PureJavaSerialPort.java:1243)
	at java.lang.Thread.run(Thread.java:748)