Index: src/org/openstreetmap/josm/tools/I18n.java
===================================================================
--- src/org/openstreetmap/josm/tools/I18n.java  (revision 4170)
+++ src/org/openstreetmap/josm/tools/I18n.java  (working copy)
@@ -118,8 +118,8 @@
         "OptionPane.noButtonText",
         "OptionPane.cancelButtonText"
     };
-    private static HashMap<String, String> strings = null;
-    private static HashMap<String, String[]> pstrings = null;
+    private static HashMap<String, String> strings = new HashMap<String, String>();
+    private static HashMap<String, String[]> pstrings = new HashMap<String, String[]>();
     private static HashMap<String, PluralMode> languages = new HashMap<String, PluralMode>();
 
     /**
@@ -406,8 +406,8 @@
     {
         if(l.equals("en") || l.equals("en_US"))
         {
-            strings = null;
-            pstrings = null;
+            strings.clear();
+            pstrings.clear();
             pluralMode = PluralMode.MODE_NOTONE;
             return true;
         }
@@ -607,8 +607,8 @@
                     System.out.println(tr("Unable to find translation for the locale {0}. Reverting to {1}.",
                             l.getDisplayName(), Locale.getDefault().getDisplayName()));
                 } else {
-                    strings = null;
-                    pstrings = null;
+                    strings.clear();
+                    pstrings.clear();
                 }
             }
         }