### Description

`from employees | eval x = 1 | keep x` results in 

```
Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because the return value of "org.elasticsearch.xpack.esql.planner.Layout.getChannel(org.elasticsearch.xpack.ql.expression.NameId)" is null
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.alignPageToAttributes(LocalExecutionPlanner.java:281)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planExchangeSink(LocalExecutionPlanner.java:305)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:199)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:146)
        at org.elasticsearch.xpack.esql.plugin.ComputeService.runCompute(ComputeService.java:246)
        at org.elasticsearch.xpack.esql.plugin.ComputeService$DataNodeRequestHandler.lambda$messageReceived$5(ComputeService.java:415)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.action.ActionListener$2.onResponse(ActionListener.java:177)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.action.ActionListener.completeWith(ActionListener.java:305)
        at org.elasticsearch.xpack.esql.plugin.ComputeService.lambda$acquireSearchContexts$13(ComputeService.java:280)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.index.shard.IndexShard.ensureShardSearchActive(IndexShard.java:3911)
        at org.elasticsearch.xpack.esql.plugin.ComputeService.acquireSearchContexts(ComputeService.java:278)
        at org.elasticsearch.xpack.esql.plugin.ComputeService$DataNodeRequestHandler.messageReceived(ComputeService.java:413)
        at org.elasticsearch.xpack.esql.plugin.ComputeService$DataNodeRequestHandler.messageReceived(ComputeService.java:405)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:74)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.transport.TransportService$6.doRun(TransportService.java:1023)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:983)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:33)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:983)
        at org.elasticsearch.server@8.10.0-SNAPSHOT/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
        at java.base/java.lang.Thread.run(Thread.java:1623)
```
x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/EsqlActionIT.java
Assert.assertEquals(1, results.columns().size());
        Assert.assertEquals(1, results.values().size());
        assertEquals("avg(ratio)", results.columns().get(0).name());
        assertEquals("double", results.columns().get(0).type());
        assertEquals(1, results.values().get(0).size());
        assertEquals(0.034d, (double) results.values().get(0).get(0), 0.001d);
    }
    public void testFromStatsEvalWithPragma() {
        assumeTrue("pragmas only enabled on snapshot builds", Build.current().isSnapshot());
        EsqlQueryResponse results = run("from test | stats avg_count = avg(count) | eval x = avg_count + 7");
        logger.info(results);
        Assert.assertEquals(1, results.values().size());
        assertEquals(2, results.values().get(0).size());
        assertEquals(50, (double) results.values().get(0).get(results.columns().indexOf(new ColumnInfo("x", "double"))), 1d);
        assertEquals(43, (double) results.values().get(0).get(results.columns().indexOf(new ColumnInfo("avg_count", "double"))), 1d);
    }
    public void testWhere() {
        EsqlQueryResponse results = run("from test | where count > 40");
        logger.info(results);
        Assert.assertEquals(30, results.values().size());
        var countIndex = results.columns().indexOf(new ColumnInfo("count", "long"));
        for (List<Object> values : results.values()) {
            assertThat((Long) values.get(countIndex), greaterThan(40L));
        }
    }
    public void testProjectWhere() {
        EsqlQueryResponse results = run("from test | keep count | where count > 40");
        logger.info(results);
        Assert.assertEquals(30, results.values().size());
        int countIndex = results.columns().indexOf(new ColumnInfo("count", "long"));