fix: Ignore item tax patch if old schema does not exists

erpnext/patches/v12_0/move_item_tax_to_item_tax_template.py

@@ -3,6 +3,8 @@ import json
 from six import iteritems
 
 def execute():
+	if "tax_type" not in frappe.db.get_table_columns("Item Tax"):
+		return
 	old_item_taxes = {}
 	item_tax_templates = {}
 	rename_template_to_untitled = []