Fix order button showing when order-column is set to empty string

[emptynick]

When the ConvertEmptyStringsToNull middleware is disabled, BREAD order-column will be stored as an empty string instead of null, thus the order button will be shown.

Fixes #4930

[codecov]

Codecov Report

Merging #5003 (aec7a57) into 1.4 (ccaf7e8) will not change coverage.
The diff coverage is 0.00%.

@@            Coverage Diff            @@
##                1.4    #5003   +/-   ##
=========================================
  Coverage     63.31%   63.31%           
  Complexity     1379     1379           
=========================================
  Files           194      194           
  Lines          4075     4075           
=========================================
  Hits           2580     2580           
  Misses         1495     1495           

Impacted Files	Coverage Δ	Complexity Δ
src/Http/Controllers/VoyagerBaseController.php	57.69% <0.00%> (ø)	143.00 <0.00> (ø)

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