[fix][broker] Fix IndexOutOfBoundsException in the CompactedTopicUtils

[coderzc]

Motivation

Fix IndexOutOfBoundsException in the CompactedTopicUtils

Modifications

if entries are empty, then early return

Documentation

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

Matching PR in forked repository

PR in forked repository:

[mattisonchao]

@coderzc
Is it passible add a test to cover it?

[codecov-commenter]

Codecov Report

Merging #20887 (76b3cb0) into master (69d7a2b) will decrease coverage by 0.04%.
Report is 7 commits behind head on master.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master   #20887      +/-   ##
============================================
- Coverage     73.17%   73.14%   -0.04%     
- Complexity    32231    32238       +7     
============================================
  Files          1874     1874              
  Lines        139302   139378      +76     
  Branches      15322    15329       +7     
============================================
+ Hits         101934   101947      +13     
- Misses        29311    29363      +52     
- Partials       8057     8068      +11     

Flag	Coverage Δ
inttests	24.14% <100.00%> (-0.28%)	⬇️
systests	25.11% <100.00%> (-0.10%)	⬇️
unittests	72.43% <100.00%> (-0.02%)	⬇️

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

Files Changed	Coverage Δ
.../apache/pulsar/compaction/CompactedTopicUtils.java	70.00% <100.00%> (-9.49%)	⬇️

... and 75 files with indirect coverage changes