fix(android): pullFolder shouldn't fail if folder contains empty file

[Malinskiy]

The pull of empty files can still fail since exists() check for stat verifies the presence of the file by checking the size, permissions and mtime. If all those are 0, the file will be considered non-existent.

Fixes #787

[codecov]

Codecov Report

Merging #789 (964a5bf) into develop (5796f81) will not change coverage.
The diff coverage is n/a.

❗ Current head 964a5bf differs from pull request most recent head 9585725. Consider uploading reports for the commit 9585725 to get more accurate results

@@            Coverage Diff             @@
##             develop     #789   +/-   ##
==========================================
  Coverage      59.65%   59.65%           
  Complexity       824      824           
==========================================
  Files            209      209           
  Lines           4303     4303           
  Branches         702      702           
==========================================
  Hits            2567     2567           
  Misses          1412     1412           
  Partials         324      324           

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