Index: trunk/src/org/openstreetmap/josm/gui/preferences/PreferenceTabbedPane.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/PreferenceTabbedPane.java	(revision 17315)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/PreferenceTabbedPane.java	(revision 17316)
@@ -575,6 +575,6 @@
     private int computeMaxTabWidth() {
         FontMetrics fm = getFontMetrics(getFont());
-        return settings.stream().filter(x -> x instanceof TabPreferenceSetting)
-                .mapToInt(x -> fm.stringWidth(((TabPreferenceSetting) x).getTitle())).max().orElse(120);
+        return settings.stream().filter(x -> x instanceof TabPreferenceSetting).map(x -> ((TabPreferenceSetting) x).getTitle())
+                .filter(Objects::nonNull).mapToInt(fm::stringWidth).max().orElse(120);
     }