Fixed an exception when searching for unlinked files. #18398

Job	Run time
Checkstyle	2m 14s
OpenRewrite	2m 9s
CHANGELOG.md	10s
Markdown	6s
Modernizer	1m 3s
CHANGELOG.md - only unreleased touched	15s
Code coverage	30s
Database tests	2m 26s
GUI tests	1m 32s
Validate requiremenet coverage	32s
Unit tests	7m 5s
Validate Gradle Wrapper	4s
Find merge conflicts	5s
Source branch is other than "main"	1s
upload-pr-number	8s
	18m 20s

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