load file from desktop file browser fails

Steps to reproduce:
1. Start jalview with fresh user properties.
2. once everything has loaded, close the example file windows and click all dialogs away.
3. press Ctrl/Cmd+O to open file browser.
4. browse to a file to load without touching the filetype filter dropdown menu.

Regardless of filetype, the file will not be loaded, and jalview will not report an error. An exception is reported on the stdout like:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at jalview.gui.Desktop.inputLocalFileMenuItem_actionPerformed(Desktop.java:917)
at jalview.jbgui.GDesktop$1.actionPerformed(GDesktop.java:147)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)

Since these steps are typical of those carried out by a new user, we need to patch this asap !