DataIndexer#getOptimalPartialIndex NPEs if there is no available DataIndex for the requested columns

[abaranec]

Description
When whereIn initializes and fails to find a complete index it tries to find a partial index with DataIndex.getOptimalPartialIndex. If there is no DataIndex available for the requested columns it will try to call DataIndex#isRefreshing on the null result.

Steps to reproduce

@Test
    public void testBroken() {
        final Table t = emptyTable(10).update("Hello=ii", "Goodbye = `A`+ii");
        final Table t2 = emptyTable(2).update("Hello=ii", "Goodbye = `A`+ii");

        Path p = Paths.get("/tmp/Bagel");
        p.toFile().mkdirs();
        Path part = p.resolve("Part=Apple");
        part.toFile().mkdirs();
        io.deephaven.parquet.table.ParquetTools.writeTable(t, part.resolve("table.parquet").toFile());

        part = p.resolve("Part=Tomato");
        part.toFile().mkdirs();
        io.deephaven.parquet.table.ParquetTools.writeTable(t, part.resolve("table.parquet").toFile());

        Table qq = t.whereIn(t2, "Goodbye");

        final Table readback = io.deephaven.parquet.table.ParquetTools.readTable(p.toFile(), io.deephaven.parquet.table.ParquetInstructions.builder()
                .setFileLayout(io.deephaven.parquet.table.ParquetInstructions.ParquetFileLayout.KV_PARTITIONED).build());

        readback.whereIn(qq, "Goodbye");
    }

Expected results

The whereIn does the right thing

Actual results

NPE

Versions

• Deephaven: 0.34.0