Disallow empty arrays in maximum/minimum

[jishnub]

This mirrors the behavior of Arrays:
Currently:

julia> maximum(Fill(3, 0))
3

After this PR

julia> maximum(fill(3, 0))
ERROR: MethodError: reducing over an empty collection is not allowed; consider supplying `init` to the reducer

julia> maximum(Fill(3, 0))
ERROR: ArgumentError: reducing over an empty collection is not allowed; consider supplying `init` to the reducer

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.91%. Comparing base (6f61dc3) to head (d51c230).
⚠️ Report is 24 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #391   +/-   ##
=======================================
  Coverage   99.91%   99.91%           
=======================================
  Files           8        8           
  Lines        1147     1149    +2     
=======================================
+ Hits         1146     1148    +2     
  Misses          1        1           

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