SUBMARINE-1141. Create experiment image dropdown list UI improvement

[cdmikechen]

What is this PR for?

Fix dropdown bug

What type of PR is it?

Bug Fix

Todos

• - Fix the displayed bug
• - Avoid duplicates or empties in dropdown list

What is the Jira issue?

https://issues.apache.org/jira/browse/SUBMARINE-1141

How should this be tested?

See screenshot

Screenshots (if appropriate)

Before:

After:

Questions:

• Do the license files need updating? No
• Are there breaking changes for older versions? No
• Does this need new documentation? No

[codecov]

Codecov Report

Merging #1087 (ba55238) into master (b0d96b3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1087   +/-   ##
=======================================
  Coverage   67.27%   67.27%           
=======================================
  Files         128      128           
  Lines        6224     6224           
=======================================
  Hits         4187     4187           
  Misses       2037     2037           

Flag	Coverage Δ
python-integration	54.20% <ø> (ø)
python-unit	48.00% <ø> (ø)

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