InvalidSchemaException While Saving ALSModel

After fitting an ALSModel, get following error while saving the model:

Caused by: org.apache.parquet.schema.InvalidSchemaException: A group type can not be empty. Parquet does not support empty group without leaves. Empty group: spark_schema

Exactly the same code ran ok on 2.2.1.

Same issue also occurs on other ALSModels we have.

To reproduce

Get ALSExample: https://github.com/apache/spark/blob/master/examples/src/main/scala/org/apache/spark/examples/ml/ALSExample.scala and add the following line to save the model right before "spark.stop".

   model.write.overwrite().save("SparkExampleALSModel") 

Stack Trace

Exception in thread "main" java.lang.ExceptionInInitializerError
at org.apache.spark.sql.execution.datasources.parquet.ParquetWriteSupport$$anonfun$setSchema$2.apply(ParquetWriteSupport.scala:444)
at org.apache.spark.sql.execution.datasources.parquet.ParquetWriteSupport$$anonfun$setSchema$2.apply(ParquetWriteSupport.scala:444)
at scala.collection.immutable.List.foreach(List.scala:392)
at org.apache.spark.sql.execution.datasources.parquet.ParquetWriteSupport$.setSchema(ParquetWriteSupport.scala:444)
at org.apache.spark.sql.execution.datasources.parquet.ParquetFileFormat.prepareWrite(ParquetFileFormat.scala:112)
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.write(FileFormatWriter.scala:140)
at org.apache.spark.sql.execution.datasources.InsertIntoHadoopFsRelationCommand.run(InsertIntoHadoopFsRelationCommand.scala:154)
at org.apache.spark.sql.execution.command.DataWritingCommandExec.sideEffectResult$lzycompute(commands.scala:104)
at org.apache.spark.sql.execution.command.DataWritingCommandExec.sideEffectResult(commands.scala:102)
at org.apache.spark.sql.execution.command.DataWritingCommandExec.doExecute(commands.scala:122)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:131)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:127)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:127)
at org.apache.spark.sql.execution.QueryExecution.toRdd$lzycompute(QueryExecution.scala:80)
at org.apache.spark.sql.execution.QueryExecution.toRdd(QueryExecution.scala:80)
at org.apache.spark.sql.DataFrameWriter$$anonfun$runCommand$1.apply(DataFrameWriter.scala:654)
at org.apache.spark.sql.DataFrameWriter$$anonfun$runCommand$1.apply(DataFrameWriter.scala:654)
at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:77)
at org.apache.spark.sql.DataFrameWriter.runCommand(DataFrameWriter.scala:654)
at org.apache.spark.sql.DataFrameWriter.saveToV1Source(DataFrameWriter.scala:273)
at org.apache.spark.sql.DataFrameWriter.save(DataFrameWriter.scala:267)
at org.apache.spark.sql.DataFrameWriter.save(DataFrameWriter.scala:225)
at org.apache.spark.ml.recommendation.ALSModel$ALSModelWriter.saveImpl(ALS.scala:510)
at org.apache.spark.ml.util.MLWriter.save(ReadWrite.scala:103)
at com.vitalmove.model.ALSExample$.main(ALSExample.scala:83)
at com.vitalmove.model.ALSExample.main(ALSExample.scala)
Caused by: org.apache.parquet.schema.InvalidSchemaException: A group type can not be empty. Parquet does not support empty group without leaves. Empty group: spark_schema
at org.apache.parquet.schema.GroupType.<init>(GroupType.java:92)
at org.apache.parquet.schema.GroupType.<init>(GroupType.java:48)
at org.apache.parquet.schema.MessageType.<init>(MessageType.java:50)
at org.apache.parquet.schema.Types$MessageTypeBuilder.named(Types.java:1256)
at org.apache.spark.sql.execution.datasources.parquet.ParquetSchemaConverter$.<init>(ParquetSchemaConverter.scala:567)
at org.apache.spark.sql.execution.datasources.parquet.ParquetSchemaConverter$.<clinit>(ParquetSchemaConverter.scala)