fix(stock): group the Stock Ledger opening-balance dimension query

get_opening_balance_for_inv_dimension selected item_code and warehouse alongside Sum() aggregates with no GROUP BY, which PostgreSQL rejects ('column ...item_code must appear in the GROUP BY clause'). Add GROUP BY item_code, warehouse. The query already returns early unless a single item and warehouse is selected, so this stays one row with identical values on MariaDB while becoming valid on Postgres.

erpnext/stock/report/stock_ledger/stock_ledger.py

@@ -822,6 +822,8 @@ def get_opening_balance_for_inv_dimension(filters, inv_dimension_wise_value):
 		else:
 			query = query.where(sl_doctype[key] == value)
 
+	query = query.groupby(sl_doctype.item_code, sl_doctype.warehouse)
+
 	opening_data = query.run(as_dict=True)
 
 	if opening_data: