fix: Tax withholding related fixes
diff --git a/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py b/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py
index 84c2c9a..61f52a1 100644
--- a/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py
+++ b/erpnext/accounts/doctype/tax_withholding_category/tax_withholding_category.py
@@ -425,7 +425,10 @@
 		):
 			# Get net total again as TDS is calculated on net total
 			# Grand is used to just check for threshold breach
-			net_total = frappe.db.get_value("Purchase Invoice", invoice_filters, "sum(net_total)") or 0.0
+			net_total = 0
+			if vouchers:
+				net_total = frappe.db.get_value("Purchase Invoice", invoice_filters, "sum(net_total)")
+
 			net_total += inv.net_total
 			supp_credit_amt = net_total - cumulative_threshold