Don't warn about fallback unless we need to

[jonjohnsonjr]

We were hitting this warning when listing an empty repository, which
doesn't make sense.

[codecov-commenter]

Codecov Report

Merging #996 (ac93bb2) into main (83f4080) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #996      +/-   ##
==========================================
- Coverage   75.19%   75.17%   -0.02%     
==========================================
  Files         107      107              
  Lines        5064     5064              
==========================================
- Hits         3808     3807       -1     
- Misses        711      712       +1     
  Partials      545      545              

Impacted Files	Coverage Δ
pkg/v1/google/list.go	70.49% <0.00%> (-0.82%)	⬇️

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