fix: cannot create debit note with zero qty

[nextchamp-saqib]

It is possible to create a Credit Note to adjust the amount without discounting the quantity. The same is not possible for Debit Notes. This PR aims to fix that.

[codecov]

Codecov Report

Merging #28994 (79ccf80) into develop (56b9ad8) will increase coverage by 0.01%.
The diff coverage is 66.66%.

@@             Coverage Diff             @@
##           develop   #28994      +/-   ##
===========================================
+ Coverage    55.68%   55.70%   +0.01%     
===========================================
  Files         1129     1129              
  Lines        67471    67473       +2     
===========================================
+ Hits         37574    37583       +9     
+ Misses       29897    29890       -7     

Impacted Files	Coverage Δ
erpnext/controllers/taxes_and_totals.py	97.46% <50.00%> (-0.19%)	⬇️
erpnext/controllers/accounts_controller.py	83.93% <100.00%> (ø)
erpnext/utilities/product.py	14.70% <0.00%> (-35.30%)	⬇️
erpnext/shopping_cart/product_info.py	30.30% <0.00%> (-21.22%)	⬇️
...ctype/woocommerce_settings/woocommerce_settings.py	80.00% <0.00%> (-4.00%)	⬇️
.../report/bom_operations_time/bom_operations_time.py	93.33% <0.00%> (-3.34%)	⬇️
...e/shopping_cart_settings/shopping_cart_settings.py	65.38% <0.00%> (-1.93%)	⬇️
...r/doctype/leave_ledger_entry/leave_ledger_entry.py	90.16% <0.00%> (-1.64%)	⬇️
.../hr/doctype/upload_attendance/upload_attendance.py	44.69% <0.00%> (-1.52%)	⬇️
erpnext/shopping_cart/product_query.py	61.19% <0.00%> (-1.50%)	⬇️
... and 20 more