[frontend] Fix loading issue when exporting as an image or PDF in the opposite theme mode (#9231 #9011)

[CelineSebe]

Proposed changes

• Always exporting to false when it's finished

Related issues

• Screen greyed out when exporting a workspace to light image #9231
• Problem when exporting TTP matrix in image and light mode #9011

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case (coverage and e2e)
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.34%. Comparing base (e4728c3) to head (e70b409).
Report is 14 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9474      +/-   ##
==========================================
- Coverage   65.34%   65.34%   -0.01%     
==========================================
  Files         624      624              
  Lines       59697    59697              
  Branches     6687     6685       -2     
==========================================
- Hits        39011    39010       -1     
- Misses      20686    20687       +1     

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[marieflorescontact]

locally tested for workspaces export and TTP matrix exports