Ensure we can handle messages with empty payloads that have properties

[kellyfj]

NOTE: Working with folks at StreamNative to use this to validate behavior when a message is received with an empty payload but non-empty properties.

(If this PR fixes a github issue, please add Fixes #<xyz>.)

Fixes #

(or if this PR is one task of a github issue, please add Master Issue: #<xyz> to link to the master issue.)

Master Issue: #

Motivation

Explain here the context, and why you're making that change. What is the problem you're trying to solve.

Modifications

Describe the modifications you've done.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API: (yes / no)
• The schema: (yes / no / don't know)
• The default values of configurations: (yes / no)
• The wire protocol: (yes / no)

Documentation

• Does this pull request introduce a new feature? (yes / no)
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• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[crossoverJie]

time="2025-10-29T05:51:13Z" level=info msg="Created producer" cnx="127.0.0.1:40770 -> 127.0.0.1:6650" producerID=1 producer_name=standalone-0-391 topic="persistent://public/default/my-topic-461702774"
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
    reader_test.go:205: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsar/reader_test.go:205
        	Error:      	Not equal: 
        	            	expected: <nil>(<nil>)
        	            	actual  : []uint8([]byte{})
        	Test:       	TestReaderEmptyPayloadNonemptyProps
time="2025-10-29T05:51:13Z" level=info msg="Producer is shutting down. Close the reconnect event loop" producerID=1 producer_name=standalone-0-391 topic="persistent://public/default/my-topic-461702774"
time="2025-10-29T05:51:13Z" level=info msg="Closing producer" producerID=1 producer_name=standalone-0-391 topic="persistent://public/default/my-topic-461702774"
time="2025-10-29T05:51:13Z" level=info msg="Closed producer" producerID=1 producer_name=standalone-0-391 topic="persistent://public/default/my-topic-461702774"
time="2025-10-29T05:51:13Z" level=info msg="Closing consumer=1" consumerID=1 name= subscription=reader-dyiag topic="persistent://public/default/my-topic-461702774"
time="2025-10-29T05:51:13Z" level=info msg="Closed consumer" consumerID=1 name= subscription=reader-dyiag topic="persistent:public/default/my-topic-461702774"
--- FAIL: TestReaderEmptyPayloadNonemptyProps (0.09s)

Please handle the exception.

[RobertIndie]

I think this PR was created to reproduce the bug that was fixed in #1435. The corresponding test was already added in that PR, so this one can be closed.