[3.6] Fix issue #4190 (#4197).

[asvetlov]

(cherry picked from commit 564d9cc)

Co-authored-by: polcak ipolcak@fit.vutbr.cz

[codecov-io]

Codecov Report

Merging #4235 into 3.6 will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              3.6    #4235      +/-   ##
==========================================
- Coverage   97.97%   97.96%   -0.02%     
==========================================
  Files          44       44              
  Lines        8886     8886              
  Branches     1392     1392              
==========================================
- Hits         8706     8705       -1     
- Misses         71       72       +1     
  Partials      109      109

Impacted Files	Coverage Δ
aiohttp/web_fileresponse.py	97.72% <0%> (-0.57%)	⬇️

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