HBASE-29066 Fix NPE in rits.jsp when regions are not open

[junegunn]

With the patch, the location of the unassigned regions are shown as "null". I added a method to RegionStateNode for the null-check, but if you prefer to do without it, I can change the expressions in the jsp file instead.

[Apache-HBase]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 0s		Docker mode activated.
-1 ❌	docker	0m 3s		Docker failed to build run-specific yetus/hbase:tp-16566}.

Subsystem	Report/Notes
GITHUB PR	#6594
Console output	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-6594/3/console
versions	git=2.17.1
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[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 31s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	hbaseanti	0m 0s		Patch does not have any anti-patterns.
			_ master Compile Tests _
+1 💚	mvninstall	3m 39s		master passed
+1 💚	compile	3m 8s		master passed
+1 💚	checkstyle	0m 37s		master passed
+1 💚	spotbugs	1m 33s		master passed
+1 💚	spotless	0m 46s		branch has no errors when running spotless:check.
			_ Patch Compile Tests _
+1 💚	mvninstall	3m 15s		the patch passed
+1 💚	compile	4m 0s		the patch passed
+1 💚	javac	4m 0s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 46s		the patch passed
+1 💚	spotbugs	2m 6s		the patch passed
+1 💚	hadoopcheck	12m 54s		Patch does not cause any errors with Hadoop 3.3.6 3.4.0.
+1 💚	spotless	1m 17s		patch has no errors when running spotless:check.
			_ Other Tests _
+1 💚	asflicense	0m 24s		The patch does not generate ASF License warnings.
		43m 19s

Subsystem	Report/Notes
Docker	ClientAPI=1.43 ServerAPI=1.43 base: https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-6594/3/artifact/yetus-general-check/output/Dockerfile
GITHUB PR	#6594
Optional Tests	dupname asflicense javac spotbugs checkstyle codespell detsecrets compile hadoopcheck hbaseanti spotless
uname	Linux 3db800c1dd77 5.4.0-1103-aws #111~18.04.1-Ubuntu SMP Tue May 23 20:04:10 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / e10af6f
Default Java	Eclipse Adoptium-17.0.11+9
Max. process+thread count	84 (vs. ulimit of 30000)
modules	C: hbase-server U: hbase-server
Console output	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-6594/3/console
versions	git=2.34.1 maven=3.9.8 spotbugs=4.7.3
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