fix: disable sales order cancellation if linked to draft invoice (#26125)

diff --git a/erpnext/selling/doctype/sales_order/sales_order.py b/erpnext/selling/doctype/sales_order/sales_order.py
index 551f715..41f57a3 100755
--- a/erpnext/selling/doctype/sales_order/sales_order.py
+++ b/erpnext/selling/doctype/sales_order/sales_order.py
@@ -233,7 +233,7 @@
 		# Checks Sales Invoice
 		submit_rv = frappe.db.sql_list("""select t1.name
 			from `tabSales Invoice` t1,`tabSales Invoice Item` t2
-			where t1.name = t2.parent and t2.sales_order = %s and t1.docstatus = 1""",
+			where t1.name = t2.parent and t2.sales_order = %s and t1.docstatus < 2""",
 			self.name)
 
 		if submit_rv:
diff --git a/erpnext/selling/doctype/sales_order/test_sales_order.py b/erpnext/selling/doctype/sales_order/test_sales_order.py
index 9873710..974648d 100644
--- a/erpnext/selling/doctype/sales_order/test_sales_order.py
+++ b/erpnext/selling/doctype/sales_order/test_sales_order.py
@@ -1217,6 +1217,19 @@
 		# To test if the SO does NOT have a Blanket Order
 		self.assertEqual(so_doc.items[0].blanket_order, None)
 
+	def test_so_cancellation_when_si_drafted(self):
+		"""
+			Test to check if Sales Order gets cancelled if Sales Invoice is in Draft state
+			Expected result: sales order should not get cancelled 
+		"""
+		so = make_sales_order()
+		so.submit()
+		si = make_sales_invoice(so.name)
+		si.save()
+
+		self.assertRaises(frappe.ValidationError, so.cancel)
+
+
 
 def make_sales_order(**args):
 	so = frappe.new_doc("Sales Order")