fix: Broken pop-up and references to non-existent field

- `child_fieldname` misspelled causing broken pop up to fetch overdue payments
- `sales_invoice` referenced in dunning fields, which has been removed
- Fetch `customer_name` from `customer` link field

erpnext/accounts/doctype/dunning/dunning.js

@@ -72,7 +72,7 @@ frappe.ui.form.on("Dunning", {
 						company: frm.doc.company
 					},
 					allow_child_item_selection: true,
-					child_fielname: "payment_schedule",
+					child_fieldname: "payment_schedule",
 					child_columns: ["due_date", "outstanding"],
 				});
 			});

erpnext/accounts/doctype/dunning/dunning.json

@@ -75,7 +75,7 @@
    "print_hide": 1
   },
   {
-   "fetch_from": "sales_invoice.customer_name",
+   "fetch_from": "customer.customer_name",
    "fieldname": "customer_name",
    "fieldtype": "Data",
    "in_list_view": 1,
@@ -184,21 +184,18 @@
    "label": "Address and Contact"
   },
   {
-   "fetch_from": "sales_invoice.address_display",
    "fieldname": "address_display",
    "fieldtype": "Small Text",
    "label": "Address",
    "read_only": 1
   },
   {
-   "fetch_from": "sales_invoice.contact_display",
    "fieldname": "contact_display",
    "fieldtype": "Small Text",
    "label": "Contact",
    "read_only": 1
   },
   {
-   "fetch_from": "sales_invoice.contact_mobile",
    "fieldname": "contact_mobile",
    "fieldtype": "Small Text",
    "label": "Mobile No",
@@ -206,14 +203,12 @@
    "read_only": 1
   },
   {
-   "fetch_from": "sales_invoice.company_address_display",
    "fieldname": "company_address_display",
    "fieldtype": "Small Text",
    "label": "Company Address Display",
    "read_only": 1
   },
   {
-   "fetch_from": "sales_invoice.contact_email",
    "fieldname": "contact_email",
    "fieldtype": "Data",
    "label": "Contact Email",
@@ -221,7 +216,6 @@
    "read_only": 1
   },
   {
-   "fetch_from": "sales_invoice.customer",
    "fieldname": "customer",
    "fieldtype": "Link",
    "label": "Customer",
@@ -387,7 +381,7 @@
  ],
  "is_submittable": 1,
  "links": [],
- "modified": "2023-06-03 16:24:01.677026",
+ "modified": "2023-06-15 15:46:53.865712",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Dunning",