fix: 🐛 fix bug when training object detection

[aminemindee]

• Small quick fix to make training object detection working again.

[codecov]

Codecov Report

Merging #1254 (8d42ae2) into main (021d4f5) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1254      +/-   ##
==========================================
+ Coverage   95.63%   95.66%   +0.02%     
==========================================
  Files         154      154              
  Lines        6873     6873              
==========================================
+ Hits         6573     6575       +2     
+ Misses        300      298       -2     

Flag	Coverage Δ
unittests	95.66% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
doctr/datasets/datasets/base.py	91.22% <100.00%> (ø)

... and 1 file with indirect coverage changes

[felixdittrich92]

Thanks for the PR @aminemindee :)
Can we maybe add a short comment above the condition that it's only the case for a detection KIE dataset ?

BTW: file_utils.py seems not the right place for copy_tensor can we move it to https://github.com/mindee/doctr/tree/main/doctr/models/utils and add a short test ? (Because it's small but uncovered currently)

[odulcy-mindee]

As @felixdittrich92 said, just add a comment and we can merge.

We'll move copy_tensor function in another PR