fix: set rate for PO created against BO (backport #39765) (#39766)

* fix: set rate for PO created against BO

(cherry picked from commit 0e5b4e5f07)

# Conflicts:
#	erpnext/manufacturing/doctype/blanket_order/blanket_order.py

* chore: `conflicts`

---------

Co-authored-by: s-aga-r <sagarsharma.s312@gmail.com>

erpnext/manufacturing/doctype/blanket_order/blanket_order.py

@@ -65,6 +65,7 @@ def make_order(source_name):
 	def update_item(source, target, source_parent):
 		target_qty = source.get("qty") - source.get("ordered_qty")
 		target.qty = target_qty if not flt(target_qty) < 0 else 0
+		target.rate = source.get("rate")
 		item = get_item_defaults(target.item_code, source_parent.company)
 		if item:
 			target.item_name = item.get("item_name")
@@ -86,6 +87,10 @@ def make_order(source_name):
 			},
 		},
 	)
+
+	if target_doc.doctype == "Purchase Order":
+		target_doc.set_missing_values()
+
 	return target_doc