fix: job card error handling for operations field

erpnext/manufacturing/doctype/job_card/job_card.py

@@ -353,17 +353,19 @@ def get_operation_details(work_order, operation):
 
 @frappe.whitelist()
 def get_operations(doctype, txt, searchfield, start, page_len, filters):
-	if filters.get("work_order"):
-		args = {"parent": filters.get("work_order")}
-		if txt:
-			args["operation"] = ("like", "%{0}%".format(txt))
-
-		return frappe.get_all("Work Order Operation",
-			filters = args,
-			fields = ["distinct operation as operation"],
-			limit_start = start,
-			limit_page_length = page_len,
-			order_by="idx asc", as_list=1)
+	if not filters.get("work_order"):
+		frappe.msgprint(_("Please select a Work Order first."))
+		return []
+	args = {"parent": filters.get("work_order")}
+	if txt:
+		args["operation"] = ("like", "%{0}%".format(txt))
+
+	return frappe.get_all("Work Order Operation",
+		filters = args,
+		fields = ["distinct operation as operation"],
+		limit_start = start,
+		limit_page_length = page_len,
+		order_by="idx asc", as_list=1)
 
 @frappe.whitelist()
 def make_material_request(source_name, target_doc=None):