bug: crash on select contract payday

[thomas-mc-work]

When opening and immediately closing the payday date selector dropdown menu without selecting a day I get this exception, followed by an application shutdown some random actions later:

[Tue Aug 13 21:54:11 CEST 2019][ERROR][main][de.willuhn.jameica.gui.GUI.loop] main loop crashed, retry
java.lang.NullPointerException
    at org.eclipse.swt.widgets.DateTime.isDropped(Unknown Source)
    at org.eclipse.swt.widgets.DateTime.dropDownCalendar(Unknown Source)
    at org.eclipse.swt.widgets.DateTime$5.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.filterEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at de.willuhn.jameica.gui.GUI.loop(GUI.java:916)
    at de.willuhn.jameica.gui.GUI.init(GUI.java:327)
    at de.willuhn.jameica.system.Application.init(Application.java:145)
    at de.willuhn.jameica.system.Application.newInstance(Application.java:87)
    at de.willuhn.jameica.Main.main(Main.java:75)

[Tue Aug 13 21:54:13 CEST 2019][ERROR][main][de.willuhn.jameica.gui.GUI.loop] main loop crashed, retry
java.lang.NullPointerException
    at org.eclipse.swt.widgets.DateTime.isDropped(Unknown Source)
    at org.eclipse.swt.widgets.DateTime.dropDownCalendar(Unknown Source)
    at org.eclipse.swt.widgets.DateTime$5.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.filterEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at de.willuhn.jameica.gui.GUI.loop(GUI.java:916)
    at de.willuhn.jameica.gui.GUI.init(GUI.java:327)
    at de.willuhn.jameica.system.Application.init(Application.java:145)
    at de.willuhn.jameica.system.Application.newInstance(Application.java:87)
    at de.willuhn.jameica.Main.main(Main.java:75)

[Tue Aug 13 21:54:14 CEST 2019][ERROR][main][de.willuhn.jameica.gui.GUI.loop] main loop crashed, retry
java.lang.NullPointerException
    at org.eclipse.swt.widgets.DateTime.isDropped(Unknown Source)
    at org.eclipse.swt.widgets.DateTime.dropDownCalendar(Unknown Source)
    at org.eclipse.swt.widgets.DateTime$5.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.filterEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at de.willuhn.jameica.gui.GUI.loop(GUI.java:916)
    at de.willuhn.jameica.gui.GUI.init(GUI.java:327)
    at de.willuhn.jameica.system.Application.init(Application.java:145)
    at de.willuhn.jameica.system.Application.newInstance(Application.java:87)
    at de.willuhn.jameica.Main.main(Main.java:75)

[Tue Aug 13 21:54:15 CEST 2019][ERROR][main][de.willuhn.jameica.gui.GUI.loop] main loop crashed, retry
java.lang.NullPointerException
    at org.eclipse.swt.widgets.DateTime.isDropped(Unknown Source)
    at org.eclipse.swt.widgets.DateTime.dropDownCalendar(Unknown Source)
    at org.eclipse.swt.widgets.DateTime$5.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.filterEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at de.willuhn.jameica.gui.GUI.loop(GUI.java:916)
    at de.willuhn.jameica.gui.GUI.init(GUI.java:327)
    at de.willuhn.jameica.system.Application.init(Application.java:145)
    at de.willuhn.jameica.system.Application.newInstance(Application.java:87)
    at de.willuhn.jameica.Main.main(Main.java:75)