FIX: Return null from single-element bopGet when element is not found

src/main/java/net/spy/memcached/v2/AsyncArcusCommands.java

@@ -1321,10 +1321,8 @@ public void receivedStatus(OperationStatus status) {
           case SUCCESS:
             break;
           case ERR_NOT_FOUND:
-            result.set(null);
-            break;
           case ERR_NOT_FOUND_ELEMENT:
-            result.set(new BTreeElement<>(bKey, null, null));
+            result.set(null);
             break;
           case CANCELLED:
             future.internalCancel();

src/main/java/net/spy/memcached/v2/AsyncArcusCommandsIF.java

@@ -685,8 +685,7 @@ ArcusFuture<Map.Entry<Boolean, BTreeElement<T>>> bopUpsertAndGetTrimmed(
    * @param bKey bKey of the element to get
    * @param args arguments for get operation
    * @return the {@code BTreeElement} if found,
-   * {@code BTreeElement} with null value and null eFlag if element is not found but key exists,
-   * {@code null} if key is not found
+   * {@code null} if the key or element is not found
    */
   ArcusFuture<BTreeElement<T>> bopGet(String key, BKey bKey, BopGetArgs args);
 

src/test/java/net/spy/memcached/v2/BTreeAsyncArcusCommandsTest.java

@@ -249,13 +249,8 @@ void bopGetWithDelete() throws Exception {
         // then
         .thenAccept(element -> assertEquals(ELEMENTS.get(1), element))
         .thenCompose(v -> async.bopGet(key, BKey.of(2L), BopGetArgs.DEFAULT))
-        .thenAccept(element -> {
-          // ELEMENT NOT FOUND
-          assertNotNull(element);
-          assertEquals(BKey.of(2L), element.getBKey());
-          assertNull(element.getValue());
-          assertNull(element.getEFlag());
-        })
+        // ELEMENT NOT FOUND
+        .thenAccept(Assertions::assertNull)
         .toCompletableFuture()
         .get(300, TimeUnit.MILLISECONDS);
   }
@@ -1696,10 +1691,7 @@ void bopDeleteSuccess() throws ExecutionException, InterruptedException, Timeout
           assertTrue(result);
           return async.bopGet(key, bKey, BopGetArgs.DEFAULT);
         })
-        .thenAccept(result -> {
-          assertNotNull(result);
-          assertNull(result.getValue());
-        })
+        .thenAccept(Assertions::assertNull)
         .toCompletableFuture()
         .get(300L, TimeUnit.MILLISECONDS);
   }