Fix the call URL input field in Developer Options

[pixlwave]

There were 2 bugs:

• The string was always set to "" when opening the screen instead of loading the current value.
• Setting the string to "" wasn't setting the override setting back to nil.

[github-actions]

	Warnings
⚠️	Some of the commits are missing ticket numbers. Please consider squashing all commits that don't have a tracking number.
⚠️	You seem to have made changes to views. Please consider adding screenshots.

Generated by 🚫 Danger Swift against 27ad2d4

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 21 lines in your changes missing coverage. Please review.

Project coverage is 77.66%. Comparing base (d54e08e) to head (27ad2d4).
Report is 2 commits behind head on develop.

Files	Patch %	Lines
...perOptionsScreen/View/DeveloperOptionsScreen.swift	0.00%	21 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3192      +/-   ##
===========================================
- Coverage    77.68%   77.66%   -0.02%     
===========================================
  Files          718      718              
  Lines        56695    56707      +12     
===========================================
- Hits         44041    44039       -2     
- Misses       12654    12668      +14     

Flag	Coverage Δ
unittests	68.30% <0.00%> (-0.02%)	⬇️

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