[cli] Fix in-flight re-login when there are no existing credentials

[TooTallNate]

This logic broke because the doLoginPrompt() return value changed in #6415 (we really need to convert this src/index.js file to TypeScript).

[codecov]

Codecov Report

Merging #6565 (c80550e) into main (a60b1b2) will increase coverage by 0.82%.
The diff coverage is n/a.

❗ Current head c80550e differs from pull request most recent head ff6f09e. Consider uploading reports for the commit ff6f09e to get more accurate results

@@            Coverage Diff             @@
##             main    #6565      +/-   ##
==========================================
+ Coverage   12.33%   13.16%   +0.82%     
==========================================
  Files         272      272              
  Lines        9807     9924     +117     
  Branches     1627     1567      -60     
==========================================
+ Hits         1210     1306      +96     
- Misses       8497     8529      +32     
+ Partials      100       89      -11     

Impacted Files	Coverage Δ
src/index.js	0.00% <0.00%> (ø)
src/util/dev/builder-cache.ts	67.46% <0.00%> (+2.99%)	⬆️
src/util/metrics.ts	57.69% <0.00%> (+3.14%)	⬆️
src/util/dev/server.ts	52.89% <0.00%> (+3.95%)	⬆️

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