Bugfix

src/lib/Interfaces/ReadOnlyCategoryIndex.vala

@@ -25,8 +25,8 @@ namespace Invercargill {
             return null;
         }
 
-        public virtual TValue @get(TKey key) throws IndexError {
-            TValue value;
+        public virtual Grouping<TKey, TValue> @get(TKey key) throws IndexError {
+            Grouping<TKey, TValue> value;
             if(try_get(key, out value)) {
                 return value;
             }