diff --git a/erpnext/hr/doctype/salary_structure/salary_structure.py b/erpnext/hr/doctype/salary_structure/salary_structure.py
index 12f8335..da69bcc 100644
--- a/erpnext/hr/doctype/salary_structure/salary_structure.py
+++ b/erpnext/hr/doctype/salary_structure/salary_structure.py
@@ -33,7 +33,7 @@
 		for employee in self.get('employees'):
 			joining_date, relieving_date = frappe.db.get_value("Employee", employee.employee,
 				["date_of_joining", "relieving_date"])
-			if employee.from_date and getdate(employee.from_date) < joining_date:
+			if employee.from_date and joining_date and getdate(employee.from_date) < joining_date:
 				frappe.throw(_("From Date {0} for Employee {1} cannot be before employee's joining Date {2}")
 					    .format(employee.from_date, employee.employee, joining_date))
 
diff --git a/erpnext/stock/get_item_details.py b/erpnext/stock/get_item_details.py
index 66ab6ac..35760fd 100644
--- a/erpnext/stock/get_item_details.py
+++ b/erpnext/stock/get_item_details.py
@@ -74,7 +74,10 @@
 
 	out.update(get_pricing_rule_for_item(args))
 
-	if args.get("doctype") in ("Sales Invoice", "Delivery Note") and out.stock_qty > 0:
+	if (args.get("doctype") == "Delivery Note" or 
+		(args.get("doctype") == "Sales Invoice" and args.get('update_stock'))) \
+		and out.warehouse and out.stock_qty > 0:
+		
 		if out.has_serial_no:
 			out.serial_no = get_serial_no(out)