[WIP] Fix crash due to no-connectivity

[mdb1]

Description

Fix crash when creating a wallet on airplane mode

Motivation and Context

Fixes https://github.com/LN-Zap/zap-iOS/issues/236

How Has This Been Tested?

The fix is not completed yet, we need 2 things to advance:

1. How do we want the "No internet" view controller to look like? I was thinking maybe an image with 2 texts (title and description) and a CTA on the bottom. Something like: [Image] Something went wrong Seems like you are not connected to the internet [TRY AGAIN]
2. What should we do with iOS versions < 12?

Screenshots (if appropriate):

Will add when I code the new error screen

Types of changes

• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [X] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[codecov-io]

Codecov Report

Merging #346 into master will decrease coverage by 0.00%. The diff coverage is 0.00%.

@@            Coverage Diff            @@
##           master    #346      +/-   ##
=========================================
- Coverage    6.68%   6.67%   -0.01%     
=========================================
  Files         233     234       +1     
  Lines        8259    8271      +12     
=========================================
  Hits          552     552              
- Misses       7707    7719      +12     

Impacted Files	Coverage Δ
Library/Helper/NetworkConnection.swift	0.00% <0.00%> (ø)

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