Fix build error in no_std env

99  | / decl_storage! {
100 | |     trait Store for Module<T: Trait> as Assets {
101 | |         /// The number of units of assets held by any given account.
102 | |         Balances: map (AssetId, T::AccountId) => T::Balance;
...   |
105 | |     }
106 | | }
Vec not found in this scope