YARN-11608. Fix QueueCapacityVectorInfo NPE when accessible labels config is used.

[brumi1024]

Description of PR

Added a null check to avoid the NPE when accessible labels config is used.

How was this patch tested?

Unit test + brought up a cluster.

For code changes:

• Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• Object storage: have the integration tests been executed and the endpoint declared according to the connector-specific documentation?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 28s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 1s		codespell was not available.
+0 🆗	detsecrets	0m 1s		detect-secrets was not available.
+0 🆗	jsonlint	0m 1s		jsonlint was not available.
+0 🆗	xmllint	0m 1s		xmllint was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	test4tests	0m 0s		The patch appears to include 6 new or modified test files.
			_ trunk Compile Tests _
+1 💚	mvninstall	32m 17s		trunk passed
+1 💚	compile	0m 42s		trunk passed with JDK Ubuntu-11.0.20.1+1-post-Ubuntu-0ubuntu120.04
+1 💚	compile	0m 37s		trunk passed with JDK Private Build-1.8.0_382-8u382-ga-1~20.04.1-b05
+1 💚	checkstyle	0m 38s		trunk passed
+1 💚	mvnsite	0m 41s		trunk passed
+1 💚	javadoc	0m 45s		trunk passed with JDK Ubuntu-11.0.20.1+1-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	0m 38s		trunk passed with JDK Private Build-1.8.0_382-8u382-ga-1~20.04.1-b05
+1 💚	spotbugs	1m 18s		trunk passed
+1 💚	shadedclient	21m 6s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 31s		the patch passed
+1 💚	compile	0m 35s		the patch passed with JDK Ubuntu-11.0.20.1+1-post-Ubuntu-0ubuntu120.04
+1 💚	javac	0m 35s		the patch passed
+1 💚	compile	0m 30s		the patch passed with JDK Private Build-1.8.0_382-8u382-ga-1~20.04.1-b05
+1 💚	javac	0m 30s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 27s		the patch passed
+1 💚	mvnsite	0m 31s		the patch passed
+1 💚	javadoc	0m 32s		the patch passed with JDK Ubuntu-11.0.20.1+1-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	0m 29s		the patch passed with JDK Private Build-1.8.0_382-8u382-ga-1~20.04.1-b05
+1 💚	spotbugs	1m 15s		the patch passed
+1 💚	shadedclient	20m 47s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	85m 46s		hadoop-yarn-server-resourcemanager in the patch passed.
+1 💚	asflicense	0m 29s		The patch does not generate ASF License warnings.
		173m 19s

Subsystem	Report/Notes
Docker	ClientAPI=1.43 ServerAPI=1.43 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-6250/1/artifact/out/Dockerfile
GITHUB PR	#6250
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets jsonlint xmllint
uname	Linux 058e3b88fff7 4.15.0-213-generic #224-Ubuntu SMP Mon Jun 19 13:30:12 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / ffa239b
Default Java	Private Build-1.8.0_382-8u382-ga-1~20.04.1-b05
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.20.1+1-post-Ubuntu-0ubuntu120.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_382-8u382-ga-1~20.04.1-b05
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-6250/1/testReport/
Max. process+thread count	949 (vs. ulimit of 5500)
modules	C: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager U: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-6250/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[tomicooler]

Thanks for the fix. LGTM.