Fix conv for empty arrays

[wheeheee]

Fixes #168 and adds tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.13%. Comparing base (d08699a) to head (12ca69f).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #628   +/-   ##
=======================================
  Coverage   98.13%   98.13%           
=======================================
  Files          19       19           
  Lines        3277     3277           
=======================================
  Hits         3216     3216           
  Misses         61       61           

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[martinholters]

LGTM, just could maybe use a test for conv of two empty arrays. @test conv(B, B; algorithm) == B might do the trick?
Should we include a version bump here and release?

[wheeheee]

Yeah, sounds good.