[Admin] ui/toast fix

[elia]

Summary

There was a missing .join.

Checklist

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• I have written a thorough PR description.
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[kennyadsl]

👍

[codecov]

Codecov Report

Merging #5250 (b1763e7) into nebulab/admin (845a2af) will increase coverage by 0.27%.
The diff coverage is n/a.

@@                Coverage Diff                @@
##           nebulab/admin    #5250      +/-   ##
=================================================
+ Coverage          88.38%   88.66%   +0.27%     
=================================================
  Files                593      564      -29     
  Lines              14414    13903     -511     
=================================================
- Hits               12740    12327     -413     
+ Misses              1674     1576      -98     

see 29 files with indirect coverage changes

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