fix: always create parameter json field

[pkdotson]

SUMMARY

this pr fixes and issue where the empty catalog for gsheets can be processed as valid in the backend validation method.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Go to dbconnection modal and without entering anything in the fields try hitting saved. It should not allow you to move on to the next step.

TESTING INSTRUCTIONS

after

Screen.Recording.2022-05-02.at.11.00.19.AM.mov

ADDITIONAL INFORMATION

• Has associated issue:
• 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 #19899 (5413375) into master (ce01ce9) will decrease coverage by 11.88%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master   #19899       +/-   ##
===========================================
- Coverage   66.44%   54.55%   -11.89%     
===========================================
  Files        1721     1718        -3     
  Lines       64548    64363      -185     
  Branches     6811     6742       -69     
===========================================
- Hits        42890    35116     -7774     
- Misses      19925    27536     +7611     
+ Partials     1733     1711       -22     

Flag	Coverage Δ
hive	53.72% <0.00%> (-0.01%)	⬇️
mysql	?
postgres	?
presto	53.58% <0.00%> (-0.01%)	⬇️
python	58.02% <100.00%> (-24.61%)	⬇️
sqlite	?
unit	49.44% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
superset/db_engine_specs/gsheets.py	69.69% <100.00%> (-5.82%)	⬇️
superset/utils/dashboard_import_export.py	0.00% <0.00%> (-100.00%)	⬇️
superset/key_value/commands/upsert.py	0.00% <0.00%> (-89.59%)	⬇️
superset/key_value/commands/update.py	0.00% <0.00%> (-89.37%)	⬇️
superset/key_value/commands/delete.py	0.00% <0.00%> (-85.30%)	⬇️
superset/key_value/commands/delete_expired.py	0.00% <0.00%> (-80.77%)	⬇️
superset/dashboards/commands/importers/v0.py	15.62% <0.00%> (-76.25%)	⬇️
superset/datasets/commands/update.py	25.88% <0.00%> (-68.24%)	⬇️
superset/datasets/commands/create.py	30.18% <0.00%> (-67.93%)	⬇️
superset/datasets/commands/importers/v0.py	24.03% <0.00%> (-67.45%)	⬇️
... and 344 more

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