fix: get income tax slab only if tax compoents are applicable (backport #394)

[mergify]

This is an automatic backport of pull request #394 done by Mergify.

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[codecov-commenter]

Codecov Report

Merging #404 (7846772) into version-14-hotfix (c40d929) will increase coverage by 0.02%.
The diff coverage is 100.00%.

Additional details and impacted files

@@                  Coverage Diff                  @@
##           version-14-hotfix     #404      +/-   ##
=====================================================
+ Coverage              71.81%   71.84%   +0.02%     
=====================================================
  Files                    181      181              
  Lines                   9350     9354       +4     
=====================================================
+ Hits                    6715     6720       +5     
+ Misses                  2635     2634       -1     

Impacted Files	Coverage Δ
hrms/payroll/doctype/salary_slip/salary_slip.py	87.85% <100.00%> (+0.15%)	⬆️