fix: wrap none type rate under flt (backport #36602) (#36604)

fix: wrap none type rate under flt (#36602)

(cherry picked from commit 627986e)

Co-authored-by: Anand Baburajan <anandbaburajan@gmail.com>

erpnext/controllers/status_updater.py

@@ -233,7 +233,7 @@ def validate_qty(self):
 				if hasattr(d, "qty") and d.qty > 0 and self.get("is_return"):
 					frappe.throw(_("For an item {0}, quantity must be negative number").format(d.item_code))
 
-				if hasattr(d, "item_code") and hasattr(d, "rate") and d.rate < 0:
+				if hasattr(d, "item_code") and hasattr(d, "rate") and flt(d.rate) < 0:
 					frappe.throw(_("For an item {0}, rate must be a positive number").format(d.item_code))
 
 				if d.doctype == args["source_dt"] and d.get(args["join_field"]):