Adds Close Method

Adds close method to ensure that realmResults are reset and that the change listener is removed.

Verified that doing the right thing and cleaning things up, fixed the fatal exception
on item deletion because the 'old' change listener is no longer called.
Resolves thorbenprimke#13

library/src/main/java/io/realm/RealmBasedRecyclerViewAdapter.java

@@ -305,6 +305,14 @@ public int getItemRealmViewType(int position) {
         return super.getItemViewType(position);
     }
 
+    /**
+     * Ensure {@link #close()} is called whenever {@link Realm#close()} is called to ensure that the
+     * {@link #realmResults} are invalidated and the change listener removed.
+     */
+    public void close() {
+        updateRealmResults(null);
+    }
+
     /**
      * Update the RealmResults associated with the Adapter. Useful when the query has been changed.
      * If the query does not change you might consider using the automaticUpdate feature.
@@ -313,15 +321,15 @@ public int getItemRealmViewType(int position) {
      */
     public void updateRealmResults(RealmResults<T> queryResults) {
         if (listener != null) {
-            if (this.realmResults != null) {
-                this.realmResults.realm.removeChangeListener(listener);
-            }
-            if (queryResults != null) {
-                queryResults.realm.addChangeListener(listener);
+            if (realmResults != null) {
+                realmResults.realm.removeChangeListener(listener);
             }
         }
 
-        this.realmResults = queryResults;
+        realmResults = queryResults;
+        if (realmResults != null) {
+            realmResults.realm.addChangeListener(listener);
+        }
 
         updateRowWrappers();
         ids = getIdsOfRealmResults();
@@ -338,7 +346,7 @@ public String createHeaderFromColumnValue(String columnValue) {
     }
 
     private List getIdsOfRealmResults() {
-        if (!animateResults || realmResults.size() == 0) {
+        if (!animateResults || realmResults == null || realmResults.size() == 0) {
             return EMPTY_LIST;
         }
 
@@ -390,6 +398,9 @@ private Object getRealmRowId(int realmIndex) {
     }
 
     private void updateRowWrappers() {
+        if (realmResults == null) {
+            return;
+        }
         if (addSectionHeaders) {
             String lastHeader = "";
             int headerCount = 0;