fix: delete old user notification settings when merging users (#26604) (

#26619)

(cherry picked from commit e97a56b)

Co-authored-by: Dhia' Shalabi <dhia.shalabi@gmail.com>

frappe/core/doctype/user/user.py

@@ -564,6 +564,10 @@ def on_trash(self):
 			frappe.throw(_("You can disable the user instead of deleting it."), frappe.LinkExistsError)
 
 	def before_rename(self, old_name, new_name, merge=False):
+		# if merging, delete the old user notification settings
+		if merge:
+			frappe.delete_doc("Notification Settings", old_name, ignore_permissions=True)
+
 		frappe.clear_cache(user=old_name)
 		self.validate_rename(old_name, new_name)