Group.<Row>globally().aggregate(Count.combineFn())) Throws Error

Trying to Count the number of rows in a window with Group and Combiner (as opposed to GroupBy "*" or a any field), but get an error:

                .apply("WindowByMinute", Window.into(FixedWindows.of(Duration.standardSeconds(60))))
                .apply("CountPerMinute", Group.globally().aggregate(Count.combineFn()))
threw:
ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.6.0:java (default-cli) on project advanced-dataflow-lab: An exception occured while executing the Java class. If the input collection uses a windowing strategy other than GlobalWindows, use Combine.globally(Count.combineFn()).withoutDefaults() instead. -\> 

Reuven Lax has indicated this is likely a bug.

Imported from Jira [BEAM-10297](https://issues.apache.org/jira/browse/BEAM-10297). Original Jira may contain additional context.
Reported by: dhodun.