fix: show sample when batch size is 1

[charlesmindee]

this PR fixes the show_sample function when the batch size is 1

Any feedback is welcome!

[codecov]

Codecov Report

Merging #787 (db4d4d5) into main (e14e643) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #787   +/-   ##
=======================================
  Coverage   96.06%   96.06%           
=======================================
  Files         130      130           
  Lines        4901     4901           
=======================================
  Hits         4708     4708           
  Misses        193      193           

Flag	Coverage Δ
unittests	96.06% <ø> (ø)

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Impacted Files	Coverage Δ
doctr/transforms/modules/base.py	94.59% <0.00%> (ø)

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[fg-mindee]

Good catch!