Comment 5 for bug 1821164

The fix pushed to trunk has some issues:

Does not completely fix the problem. To reproduce:

Run the GUI and check a location of e.g. verifypn file. Close the GUI.
Replace verifypn with some bogus (but executable) file. Run the GUI again
and go to Tools/Engine Selection. Now it throws NPE that is not handled:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
 at java.util.regex.Matcher.getTextLength(Matcher.java:1234)
 at java.util.regex.Matcher.reset(Matcher.java:308)
 at java.util.regex.Matcher.<init>(Matcher.java:228)
 at java.util.regex.Pattern.matcher(Pattern.java:1088)
....