Reduce warning logs in OIDC middleware

[reasonerjt]

If the request does not have bearer token in the header, do not decode
the empty string.
Fixes #12261

Signed-off-by: Daniel Jiang jiangd@vmware.com

[codecov]

Codecov Report

Merging #14116 (2dd499b) into master (9574f8c) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #14116      +/-   ##
==========================================
- Coverage   63.82%   63.78%   -0.04%     
==========================================
  Files         954      954              
  Lines       63866    63871       +5     
  Branches     2169     2170       +1     
==========================================
- Hits        40760    40743      -17     
- Misses      19121    19137      +16     
- Partials     3985     3991       +6     

Flag	Coverage Δ
unittests	63.78% <100.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/server/middleware/security/idtoken.go	22.58% <100.00%> (-8.46%)	⬇️
src/common/utils/oidc/helper.go	46.50% <0.00%> (-4.50%)	⬇️
...ig/vulnerability/vulnerability-config.component.ts	58.33% <0.00%> (-3.48%)	⬇️
src/controller/event/topic.go	9.00% <0.00%> (-1.81%)	⬇️
src/chartserver/utils.go	73.21% <0.00%> (-1.46%)	⬇️
...lnerability-scanning/result-bar-chart.component.ts	51.11% <0.00%> (-0.06%)	⬇️
src/pkg/exporter/system_collector.go	0.00% <0.00%> (ø)
...ry/artifact/artifact-tag/artifact-tag.component.ts	40.22% <0.00%> (+0.68%)	⬆️
src/pkg/exporter/project_collector.go	30.98% <0.00%> (+0.98%)	⬆️
... and 1 more

[wy65701436]

lgtm