Prevent users from nulling out profile values

[ColdHeat]

• Prevent users from nulling out profile values

[codecov]

Codecov Report

Merging #1125 into master will increase coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1125      +/-   ##
==========================================
+ Coverage   88.02%   88.08%   +0.06%     
==========================================
  Files          92       92              
  Lines        4944     4944              
==========================================
+ Hits         4352     4355       +3     
+ Misses        592      589       -3

Impacted Files	Coverage Δ
CTFd/schemas/teams.py	81.37% <ø> (ø)	⬆️
CTFd/schemas/users.py	95.83% <ø> (ø)	⬆️
CTFd/api/v1/teams.py	87.5% <0%> (+0.44%)	⬆️
CTFd/utils/updates/__init__.py	86.48% <0%> (+5.4%)	⬆️

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