fix: null pointer in Javascript

[beltram]

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PR Submission Checklist for internal contributors

• The PR Title

  • conforms to the style of semantic commits messages¹ supported in Wire's Github Workflow²
  • contains a reference JIRA issue number like SQPIT-764
  • answers the question: If merged, this PR will: ... ³

• The PR Description

  • is free of optional paragraphs and you have filled the relevant parts to the best of your ability

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References

1. https://sparkbox.com/foundry/semantic_commit_messages
2. https://github.com/wireapp/.github#usage
3. E.g. feat(conversation-list): Sort conversations by most emojis in the title #SQPIT-764.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (be4edd4) 73.04% compared to head (18ab45b) 73.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #461      +/-   ##
===========================================
- Coverage    73.04%   73.00%   -0.04%     
===========================================
  Files           91       91              
  Lines        15060    15086      +26     
===========================================
+ Hits         11000    11014      +14     
- Misses        4060     4072      +12     

see 9 files with indirect coverage changes

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