fix(gallery): Hide the bottom info section when no chart is being selected

[stephenLYZ]

SUMMARY

This PR improve the viz gallery that hide the bottom info section when no chart is being selected.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

after

2021-09-25.4.46.09.mov

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue: [Gallery]Hide the bottom info section when no chart is being selected #16771
• Required feature flags:
• 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

[codecov]

Codecov Report

Merging #16840 (2a06b61) into master (a341319) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master   #16840   +/-   ##
=======================================
  Coverage   77.00%   77.00%           
=======================================
  Files        1018     1018           
  Lines       54687    54688    +1     
  Branches     7461     7463    +2     
=======================================
+ Hits        42112    42113    +1     
  Misses      12331    12331           
  Partials      244      244           

Flag	Coverage Δ
javascript	71.12% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...ponents/controls/VizTypeControl/VizTypeGallery.tsx	94.85% <100.00%> (+0.02%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a341319...2a06b61. Read the comment docs.

[zhaoyongjie]

LGTM, Thanks for the improvement.