[YUNIKORN-1997] fix: yunikorn status page fails when scheduler is not healthy

[stu01509]

What is this PR for?

Fix Yunikorn status page fails when scheduler is not healthy

What type of PR is it?

• - Bug Fix
• - Improvement
• - Feature
• - Documentation
• - Hot Fix
• - Refactoring

Todos

• - Task

What is the Jira issue?

https://issues.apache.org/jira/browse/YUNIKORN-1997

How should this be tested?

Screenshots (if appropriate)

Questions:

• - The licenses files need update.
• - There is breaking changes for older versions.
• - It needs documentation.

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (6808a74) 77.65% compared to head (6887411) 77.64%.

Files	Patch %	Lines
pkg/webservice/handlers.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #718      +/-   ##
==========================================
- Coverage   77.65%   77.64%   -0.02%     
==========================================
  Files          80       80              
  Lines       13355    13357       +2     
==========================================
  Hits        10371    10371              
- Misses       2661     2663       +2     
  Partials      323      323              

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[pbacsko]

+1