Fixed invalid result adapting when no result for Optional and List types.

Author: ZorTik

core/src/main/java/me/zort/sqllib/mapping/DefaultResultAdapter.java

@@ -17,7 +17,7 @@ public Object adaptResult(Method method, QueryResult result) {
         if(returnType.equals(QueryResult.class)) {
             return result;
         } else if (isVoid(returnType) || !(result instanceof QueryRowsResult)) {
-            return null;
+            return noResult(returnType, result.isSuccessful());
         }
         QueryRowsResult<?> rows = (QueryRowsResult<?>) result;
         if (List.class.isAssignableFrom(returnType)) return rows;
@@ -38,6 +38,12 @@ public Class<?> retrieveResultType(Method method) {
         }
     }
 
+    private static <T> Object noResult(Class<T> returnType, boolean successful) {
+        if (Optional.class.isAssignableFrom(returnType)) return Optional.empty();
+        if (List.class.isAssignableFrom(returnType)) return new QueryRowsResult<T>(successful);
+        return null;
+    }
+
     // List<T>
     private static Class<?> getGenericArgument(Class<?> clazz, Type genericType, boolean throwNotFound) {
         Type[] typeParameters = ((ParameterizedType) genericType).getActualTypeArguments();