fix: fallbackLocales to false causing unexpected behaviour

[Shinyaigeek]

Fix: 1121

lingui fails to compile when fallbackLocales: false is specified in lingui configuration and msgStr is missing.
I fixed this issue.

should I add any tests?

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[codecov]

Codecov Report

Merging #1123 (f73a8f0) into main (ea00f55) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #1123   +/-   ##
=======================================
  Coverage   82.28%   82.28%           
=======================================
  Files          56       56           
  Lines        1677     1677           
  Branches      458      459    +1     
=======================================
  Hits         1380     1380           
  Misses        173      173           
  Partials      124      124           

Impacted Files	Coverage Δ
packages/cli/src/api/catalog.ts	81.48% <0.00%> (ø)

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[semoal]

LGTM, thanks for contributing mate. I'll keep merging triage: accepted bugs/features along the week and I'll release a new version next Tuesday.