Vague error message during SegmentINdexCreation if column is not found

I haven't tracked down the issue with my schema. I'm guessing I have another typo. The logs look like this. I'm going to improve the error message.

```
java.lang.RuntimeException: Caught exception during running - org.apache.pinot.plugin.ingestion.batch.standalone.SegmentGenerationJobRunner
at org.apache.pinot.spi.ingestion.batch.IngestionJobLauncher.kickoffIngestionJob(IngestionJobLauncher.java:121) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.spi.ingestion.batch.IngestionJobLauncher.runIngestionJob(IngestionJobLauncher.java:94) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.tools.admin.command.LaunchDataIngestionJobCommand.execute(LaunchDataIngestionJobCommand.java:123) [pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.tools.admin.PinotAdministrator.execute(PinotAdministrator.java:156) [pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.tools.admin.PinotAdministrator.main(PinotAdministrator.java:168) [pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
Caused by: java.lang.NullPointerException
at org.apache.pinot.core.indexsegment.immutable.ImmutableSegmentImpl.getDictionary(ImmutableSegmentImpl.java:63) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.data.readers.PinotSegmentColumnReader.(PinotSegmentColumnReader.java:40) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.BaseSingleTreeBuilder.(BaseSingleTreeBuilder.java:130) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.OffHeapSingleTreeBuilder.(OffHeapSingleTreeBuilder.java:69) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.MultipleTreesBuilder.getSingleTreeBuilder(MultipleTreesBuilder.java:140) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.MultipleTreesBuilder.build(MultipleTreesBuilder.java:118) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.segment.creator.impl.SegmentIndexCreationDriverImpl.buildStarTreeV2IfNecessary(SegmentIndexCreationDriverImpl.java:277) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.segment.creator.impl.SegmentIndexCreationDriverImpl.handlePostCreation(SegmentIndexCreationDriverImpl.java:239) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.segment.creator.impl.SegmentIndexCreationDriverImpl.build(SegmentIndexCreationDriverImpl.java:199) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.plugin.ingestion.batch.common.SegmentGenerationTaskRunner.run(SegmentGenerationTaskRunner.java:102) ~[pinot-batch-ingestion-standalone-0.4.0-SNAPSHOT-shaded.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.plugin.ingestion.batch.standalone.SegmentGenerationJobRunner.run(SegmentGenerationJobRunner.java:190) ~[pinot-batch-ingestion-standalone-0.4.0-SNAPSHOT-shaded.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.spi.ingestion.batch.IngestionJobLauncher.kickoffIngestionJob(IngestionJobLauncher.java:119) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
... 4 more
Exception caught:
java.lang.RuntimeException: Caught exception during running - org.apache.pinot.plugin.ingestion.batch.standalone.SegmentGenerationJobRunner
at org.apache.pinot.spi.ingestion.batch.IngestionJobLauncher.kickoffIngestionJob(IngestionJobLauncher.java:121) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.spi.ingestion.batch.IngestionJobLauncher.runIngestionJob(IngestionJobLauncher.java:94) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.tools.admin.command.LaunchDataIngestionJobCommand.execute(LaunchDataIngestionJobCommand.java:123) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.tools.admin.PinotAdministrator.execute(PinotAdministrator.java:156) [pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.tools.admin.PinotAdministrator.main(PinotAdministrator.java:168) [pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
Caused by: java.lang.NullPointerException
at org.apache.pinot.core.indexsegment.immutable.ImmutableSegmentImpl.getDictionary(ImmutableSegmentImpl.java:63) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.data.readers.PinotSegmentColumnReader.(PinotSegmentColumnReader.java:40) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.BaseSingleTreeBuilder.(BaseSingleTreeBuilder.java:130) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.OffHeapSingleTreeBuilder.(OffHeapSingleTreeBuilder.java:69) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.MultipleTreesBuilder.getSingleTreeBuilder(MultipleTreesBuilder.java:140) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.startree.v2.builder.MultipleTreesBuilder.build(MultipleTreesBuilder.java:118) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.segment.creator.impl.SegmentIndexCreationDriverImpl.buildStarTreeV2IfNecessary(SegmentIndexCreationDriverImpl.java:277) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.segment.creator.impl.SegmentIndexCreationDriverImpl.handlePostCreation(SegmentIndexCreationDriverImpl.java:239) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.core.segment.creator.impl.SegmentIndexCreationDriverImpl.build(SegmentIndexCreationDriverImpl.java:199) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.plugin.ingestion.batch.common.SegmentGenerationTaskRunner.run(SegmentGenerationTaskRunner.java:102) ~[pinot-batch-ingestion-standalone-0.4.0-SNAPSHOT-shaded.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.plugin.ingestion.batch.standalone.SegmentGenerationJobRunner.run(SegmentGenerationJobRunner.java:190) ~[pinot-batch-ingestion-standalone-0.4.0-SNAPSHOT-shaded.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
at org.apache.pinot.spi.ingestion.batch.IngestionJobLauncher.kickoffIngestionJob(IngestionJobLauncher.java:119) ~[pinot-all-0.4.0-SNAPSHOT-jar-with-dependencies.jar:0.4.0-SNAPSHOT-ed26e8589fe5f91d2876d417aebf23575010cc76]
... 4 more
```

Start at org.apache.pinot.core.indexsegment.immutable.ImmutableSegmentImpl.getDictionary and follow the call into PinotSegmentColumnReader, then the StarTree builders shown in the stack trace. Reproduce the SegmentIndexCreationDriverImpl path with a missing column and verify that it reports the missing column clearly instead of exposing only a NullPointerException.

Written by the indexing model from the issue text.