[backend] fix(obfuscator): review migration (#3795)

[gabriel-peze]

Proposed changes

• Fix migration V4_70 when inject_content is set at null or 'null'

Testing Instructions

1. Try to replay migration V4_70 with inject_content at null or 'null' and it shouldn't fail

Related issues

• Closes In inject view, it is indicated CMD does not support base64 obfuscation #3795

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.64%. Comparing base (0f86401) to head (b4ccb6a).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #4971   +/-   ##
=========================================
  Coverage     55.64%   55.64%           
  Complexity     4386     4386           
=========================================
  Files           984      984           
  Lines         29161    29161           
  Branches       2132     2132           
=========================================
  Hits          16227    16227           
  Misses        11995    11995           
  Partials        939      939           

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