[frontend] Fix warnings and fix linter

[guillaumejparis]

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 26.17%. Comparing base (d6fee82) to head (a4be35d). Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #915      +/-   ##
============================================
+ Coverage     25.87%   26.17%   +0.30%     
- Complexity      969      973       +4     
============================================
  Files           439      439              
  Lines         10126    10130       +4     
  Branches        482      482              
============================================
+ Hits           2620     2652      +32     
+ Misses         7444     7416      -28     
  Partials         62       62              

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[RomuDeuxfois]

UI problem