Fix setting displayname and avatar_url

[S7evinK]

As per the spec, displayname and avatar_url may be empty.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02 ⚠️

Comparison is base (a5ea928) 65.84% compared to head (b2442b9) 65.82%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3125      +/-   ##
==========================================
- Coverage   65.84%   65.82%   -0.02%     
==========================================
  Files         504      504              
  Lines       55762    55750      -12     
==========================================
- Hits        36716    36698      -18     
- Misses      15282    15284       +2     
- Partials     3764     3768       +4     

Flag	Coverage Δ
unittests	49.95% <ø> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
clientapi/routing/profile.go	49.06% <ø> (-0.05%)	⬇️

... and 8 files with indirect coverage changes

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