display invoices section field only if there are invoices

erpnext/accounts/doctype/subscriptions/subscriptions.json

@@ -647,6 +647,7 @@
    "bold": 0, 
    "collapsible": 0, 
    "columns": 0, 
+   "depends_on": "eval(doc.invoices)", 
    "fieldname": "sb_3", 
    "fieldtype": "Section Break", 
    "hidden": 0, 
@@ -715,7 +716,7 @@
  "issingle": 0, 
  "istable": 0, 
  "max_attachments": 0, 
- "modified": "2018-02-26 04:22:41.250547", 
+ "modified": "2018-02-26 04:49:46.141146", 
  "modified_by": "Administrator", 
  "module": "Accounts", 
  "name": "Subscriptions",