[fix][ml] Fix potential NPE cause future never complete.

[mattisonchao]

Motivation

Found by chance :)

I wonder if it is a real problem, but we judged it in the previous lines. I think the ex.getCause probably is null.

Modifications

• Avoid NPE

Verifying this change

• Make sure that the change passes the CI checks.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository:

[lhotari]

/pulsarbot rerun-failure-checks

[codecov-commenter]

Codecov Report

Merging #19415 (1788572) into master (3d8b52a) will increase coverage by 35.23%.
The diff coverage is 32.46%.

@@              Coverage Diff              @@
##             master   #19415       +/-   ##
=============================================
+ Coverage     27.22%   62.46%   +35.23%     
- Complexity     6264    25682    +19418     
=============================================
  Files          1644     1829      +185     
  Lines        123745   134865    +11120     
  Branches      13495    14985     +1490     
=============================================
+ Hits          33693    84245    +50552     
+ Misses        84932    42901    -42031     
- Partials       5120     7719     +2599     

Flag	Coverage Δ
inttests	25.14% <16.59%> (?)
systests	25.86% <10.45%> (+0.37%)	⬆️
unittests	59.57% <32.46%> (+42.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ker/loadbalance/extensions/BrokerRegistryImpl.java	0.00% <0.00%> (ø)
...xtensions/channel/ServiceUnitStateChannelImpl.java	1.21% <0.00%> (+1.21%)	⬆️
...balance/extensions/store/LoadDataStoreFactory.java	0.00% <0.00%> (ø)
...e/extensions/store/TableViewLoadDataStoreImpl.java	0.00% <0.00%> (ø)
...oker/service/schema/SchemaRegistryServiceImpl.java	64.05% <0.00%> (+6.83%)	⬆️
.../apache/pulsar/client/api/MessageAcknowledger.java	0.00% <ø> (ø)
...rg/apache/pulsar/client/impl/PulsarClientImpl.java	74.29% <ø> (+25.51%)	⬆️
...ent/impl/UnAckedTopicMessageRedeliveryTracker.java	7.14% <0.00%> (+7.14%)	⬆️
...pulsar/client/impl/UnAckedTopicMessageTracker.java	43.75% <0.00%> (+31.25%)	⬆️
...che/pulsar/io/elasticsearch/client/RestClient.java	84.69% <ø> (+84.69%)	⬆️
... and 1314 more