fix: null exception from adhoc metric popover

[graceguo-supercat]

SUMMARY

This PR is to fix a JS exception, which is specific to druid dataset. When user tried to add/edit Metrics for a druid dataset, JS exception is thrown.

Before

After
Show adhoc metrics popovers.

TEST PLAN

CI and manual test

[codecov]

Codecov Report

Merging #13955 (9a105f1) into master (9156f08) will increase coverage by 0.81%.
The diff coverage is 92.59%.

❗ Current head 9a105f1 differs from pull request most recent head 2aa1b0b. Consider uploading reports for the commit 2aa1b0b to get more accurate results

@@            Coverage Diff             @@
##           master   #13955      +/-   ##
==========================================
+ Coverage   77.83%   78.64%   +0.81%     
==========================================
  Files         934      935       +1     
  Lines       47320    47375      +55     
  Branches     5913     5973      +60     
==========================================
+ Hits        36831    37260     +429     
+ Misses      10346     9972     -374     
  Partials      143      143              

Flag	Coverage Δ
cypress	56.03% <73.62%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...tend/src/SqlLab/components/ScheduleQueryButton.tsx	28.12% <ø> (ø)
...et-frontend/src/SqlLab/components/TableElement.jsx	88.60% <ø> (+0.23%)	⬆️
...end/src/common/components/DropdownButton/index.tsx	24.00% <0.00%> (ø)
...rset-frontend/src/components/ProgressBar/index.tsx	100.00% <ø> (ø)
.../components/CrossFilterScopingModal/utils/index.ts	100.00% <ø> (ø)
...src/dashboard/components/PublishedStatus/index.jsx	100.00% <ø> (ø)
...dashboard/components/SliceHeaderControls/index.jsx	77.89% <ø> (ø)
...perset-frontend/src/datasource/DatasourceModal.tsx	72.58% <ø> (ø)
...ontrols/AnnotationLayerControl/AnnotationLayer.jsx	84.76% <ø> (ø)
...mponents/controls/AnnotationLayerControl/index.jsx	82.85% <ø> (ø)
... and 82 more

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[zhaoyongjie]

LGTM