fix: Modal is blinking when opening

[michael-s-molina]

SUMMARY

Fixes the modal blinking when opening.

@rusackas @junlincc

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

screen-recording-2021-08-02-at-32827-pm_yhNJpLZS.mp4

screen-recording-2021-08-02-at-32326-pm_4LdQY3DC.mp4

TESTING INSTRUCTIONS

See the before and after videos.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[suddjian]

noice

[codecov]

Codecov Report

Merging #16035 (60c52e2) into master (6095978) will decrease coverage by 0.12%.
The diff coverage is 52.83%.

❗ Current head 60c52e2 differs from pull request most recent head 95f728e. Consider uploading reports for the commit 95f728e to get more accurate results

@@            Coverage Diff             @@
##           master   #16035      +/-   ##
==========================================
- Coverage   76.79%   76.66%   -0.13%     
==========================================
  Files         990      995       +5     
  Lines       52517    52787     +270     
  Branches     6642     6694      +52     
==========================================
+ Hits        40330    40470     +140     
- Misses      11963    12092     +129     
- Partials      224      225       +1     

Flag	Coverage Δ
javascript	71.28% <52.32%> (-0.21%)	⬇️

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

Impacted Files	Coverage Δ
...ntend/src/dashboard/containers/DashboardHeader.jsx	100.00% <ø> (ø)
...ntend/src/explore/components/ExploreChartPanel.jsx	15.00% <ø> (ø)
...nd/src/explore/components/ExploreViewContainer.jsx	2.11% <0.00%> (ø)
superset-frontend/src/explore/reducers/index.js	0.00% <ø> (ø)
superset/reports/api.py	87.78% <ø> (ø)
superset-frontend/src/reports/actions/reports.js	10.86% <10.86%> (ø)
superset-frontend/src/reports/reducers/reports.js	25.00% <25.00%> (ø)
.../ReportModal/HeaderReportActionsDropdown/index.tsx	25.71% <25.71%> (ø)
...tend/src/explore/components/ExploreChartHeader.jsx	56.33% <47.05%> (-6.17%)	⬇️
...frontend/src/dashboard/components/Header/index.jsx	63.74% <54.54%> (-2.69%)	⬇️
... and 15 more

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