jp2image.cpp: check size before allocation to avoid out-of-memory errors (backport #1814)

[mergify]

This is an automatic backport of pull request #1814 done by Mergify.
Cherry-pick of 32a26ad has failed:

On branch mergify/bp/main/pr-1814
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Changes to be committed:
	modified:   tests/bugfixes/github/test_issue_1522.py
	modified:   tests/bugfixes/github/test_issue_1812.py
	modified:   tests/bugfixes/github/test_issue_ghsa_7569_phvm_vwc2.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/jp2image.cpp

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[codecov]

Codecov Report

Merging #1825 (ffde235) into main (c65941c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1825   +/-   ##
=======================================
  Coverage   60.51%   60.52%           
=======================================
  Files          96       96           
  Lines       18845    18857   +12     
  Branches     9469     9477    +8     
=======================================
+ Hits        11404    11413    +9     
+ Misses       5155     5154    -1     
- Partials     2286     2290    +4     

Impacted Files	Coverage Δ
src/jp2image.cpp	68.76% <100.00%> (-0.34%)	⬇️
src/jpgimage.cpp	70.01% <0.00%> (-0.27%)	⬇️
src/actions.cpp	61.21% <0.00%> (+0.32%)	⬆️

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