Index: trunk/src/org/openstreetmap/josm/data/validation/tests/TagChecker.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/tests/TagChecker.java	(revision 18276)
+++ trunk/src/org/openstreetmap/josm/data/validation/tests/TagChecker.java	(revision 18277)
@@ -546,5 +546,5 @@
     private static Set<String> getPresetValues(String key) {
         Set<String> res = TaggingPresets.getPresetValues(key);
-        if (res != null)
+        if (!Utils.isEmpty(res))
             return res;
         if (additionalPresetsValueData.contains(key))
@@ -561,5 +561,5 @@
      */
     public static boolean isKeyInPresets(String key) {
-        return TaggingPresets.getPresetValues(key) != null;
+        return !Utils.isEmpty(TaggingPresets.getPresetValues(key));
     }
 
Index: trunk/src/org/openstreetmap/josm/gui/tagging/presets/TaggingPresets.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/tagging/presets/TaggingPresets.java	(revision 18276)
+++ trunk/src/org/openstreetmap/josm/gui/tagging/presets/TaggingPresets.java	(revision 18277)
@@ -205,5 +205,5 @@
      * Return set of values for a key in the tagging presets
      * @param key the key
-     * @return set of values for a key in the tagging presets or null if none is found
+     * @return set of values for a key in the tagging presets
      */
     public static Set<String> getPresetValues(String key) {
@@ -211,5 +211,5 @@
         if (values != null)
             return Collections.unmodifiableSet(values);
-        return null;
+        return Collections.emptySet();
     }