Make "null decryptor" exception more informative

Forgetting to pass decryption properties when reading an encrypted column in files with plaintext footer, results in a "null decryptor" exception thrown in the ColumnChunkMetaData class. The exception text can/should be updated to point to the possible reason.

**Reporter**: [Gidon Gershinsky](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=gershinsky) / @ggershinsky
**Assignee**: [Gidon Gershinsky](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=gershinsky) / @ggershinsky

_{**Note**: *This issue was originally created as [PARQUET-2033](https://issues.apache.org/jira/browse/PARQUET-2033). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}