LoaderClient throws NPE when user presses cancel on file selection

[balazsracz]

Steps to repro:

• open firmware uploader from JMRI
• hit select file
• press cancel on the dialog

expected result: nothing happens
actual result: NPE gets printed to the console.

This is what it looks like:
2017-04-25 16:04:49,340 ptionhandler.UncaughtExceptionHandler ERROR - Uncaught Exception caught by jmri.util.exceptionhandler.UncaughtExceptionHandler [AWT-EventQueue-0]
java.lang.NullPointerException
at jmri.jmrix.openlcb.swing.downloader.LoaderPane.doRead(LoaderPane.java:95)
at jmri.jmrix.AbstractLoaderPane.lambda$0(AbstractLoaderPane.java:111)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6533)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6298)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)

It seems we don't check for the return status when getting back control from the file select dialog.

[bobjacobsen]

This was fixed in JMRI 5.3.4 by JMRI/JMRI/#111811, please close.