Fix ArrayIndexOutOfBounds for RetractableTopNFunction

// Some comments here
	@Test
	public void testCornerCase() throws Exception {
		AbstractTopNFunction func = createFunction(RankType.ROW_NUMBER, new ConstantRankRange(1, 3), false,
				false);
		OneInputStreamOperatorTestHarness<RowData, RowData> testHarness = createTestHarness(func);
		testHarness.open();
		testHarness.processElement(insertRecord("a", 1L, 1));
		testHarness.processElement(insertRecord("a", 2L, 2));
		testHarness.processElement(insertRecord("a", 3L, 2));
		testHarness.processElement(insertRecord("a", 4L, 2));
		testHarness.processElement(insertRecord("a", 5L, 3));
		testHarness.processElement(insertRecord("a", 6L, 4));
		testHarness.processElement(updateBeforeRecord("a", 2L, 2));
		testHarness.close();
	}