fix NPE caused because a null (not an empty collection) may be returned when getting markers

org.eclipse.babel.editor/src/org/eclipse/babel/editor/MessagesEditorMarkers.java

diff --git a/org.eclipse.babel.editor/src/org/eclipse/babel/editor/MessagesEditorMarkers.java b/org.eclipse.babel.editor/src/org/eclipse/babel/editor/MessagesEditorMarkers.java
index c4e6451..30e1b6f 100644
--- a/org.eclipse.babel.editor/src/org/eclipse/babel/editor/MessagesEditorMarkers.java
+++ b/org.eclipse.babel.editor/src/org/eclipse/babel/editor/MessagesEditorMarkers.java
@@ -42,9 +42,13 @@
    // private Map<String,Set<ValidationFailureEvent>> markersIndex = new HashMap();
     /** index is the name of the key. value is the collection of markers on that key */
     private Map<String, Collection<IMessageCheck>> markersIndex = new HashMap<String, Collection<IMessageCheck>>();
-    /** index is the concat of the locale and the key.
-     * value is the collection of markers for that key and that locale */
-    private Map<String, Collection<IMessageCheck>> localizedMarkersIndex = new HashMap<String, Collection<IMessageCheck>>();
+    
+	/**
+	 * Maps a localized key (a locale and key pair) to the collection of markers
+	 * for that key and that locale. If no there are no markers for the key and
+	 * locale then there will be no entry in the map.
+	 */
+    private Map<String, Collection<IMessageCheck>> localizedMarkersMap = new HashMap<String, Collection<IMessageCheck>>();
     
     /**
      * @param messagesBundleGroup
@@ -74,7 +78,7 @@
         });
     }
     
-    private String hash(Locale locale, String key) {
+    private String buildLocalizedKey(Locale locale, String key) {
     	//the '=' is hack to make sure no local=key can ever conflict
     	//with another local=key: in other words
         //it makes a hash of the combination (key+locale).
@@ -96,11 +100,11 @@
         }
         markersForKey.add(event.getCheck());
         
-        String localizedKey = hash(event.getLocale(), event.getKey());
-        markersForKey = localizedMarkersIndex.get(localizedKey);
+        String localizedKey = buildLocalizedKey(event.getLocale(), event.getKey());
+        markersForKey = localizedMarkersMap.get(localizedKey);
         if (markersForKey == null) {
         	markersForKey = new HashSet<IMessageCheck>();
-        	localizedMarkersIndex.put(localizedKey, markersForKey);
+        	localizedMarkersMap.put(localizedKey, markersForKey);
         }
         markersForKey.add(event.getCheck());
         
@@ -111,7 +115,7 @@
     
     public void clear() {
         markersIndex.clear();
-        localizedMarkersIndex.clear();
+        localizedMarkersMap.clear();
         setChanged();
         notifyObservers(this);
     }
@@ -123,8 +127,16 @@
     public Collection<IMessageCheck> getFailedChecks(String key) {
     	return markersIndex.get(key);
     }
+    
+    /**
+     * 
+     * @param key
+     * @param locale
+     * @return the collection of markers for the locale and key; the return value may be
+     * 		null if there are no markers
+     */
     public Collection<IMessageCheck> getFailedChecks(final String key, final Locale locale) {
-    	return localizedMarkersIndex.get(hash(locale, key));
+    	return localizedMarkersMap.get(buildLocalizedKey(locale, key));
     }
         
     private void validate() {

org.eclipse.babel.editor/src/org/eclipse/babel/editor/i18n/EntryRightBanner.java

diff --git a/org.eclipse.babel.editor/src/org/eclipse/babel/editor/i18n/EntryRightBanner.java b/org.eclipse.babel.editor/src/org/eclipse/babel/editor/i18n/EntryRightBanner.java
index 486b8e6..3514cd6 100644
--- a/org.eclipse.babel.editor/src/org/eclipse/babel/editor/i18n/EntryRightBanner.java
+++ b/org.eclipse.babel.editor/src/org/eclipse/babel/editor/i18n/EntryRightBanner.java
@@ -110,14 +110,16 @@
                     String key = editor.getSelectedKey();
                     Collection<IMessageCheck> checks = editor.getMarkers().getFailedChecks(
                             key, locale);
-                    for (IMessageCheck check : checks) {
-                        Action action = getCheckAction(key, check);
-                        if (action != null) {
-                            toolBarMgr.add(action);
-                            toolBarMgr.update(true);
-                            getParent().layout(true, true);
-                            isMarked = true;
-                        }
+                    if (checks != null) {
+                    	for (IMessageCheck check : checks) {
+                    		Action action = getCheckAction(key, check);
+                    		if (action != null) {
+                    			toolBarMgr.add(action);
+                    			toolBarMgr.update(true);
+                    			getParent().layout(true, true);
+                    			isMarked = true;
+                    		}
+                    	}
                     }
                     toolBarMgr.update(true);
                     getParent().layout(true, true);