No longer panic in the old subscription JSON-RPC functions if block can't be decoded

[tomaka]

In the case of a relay chain, we simply cannot sync if the block headers are in a format that can't be decoded.
However, in the case of a parachain, it is actually possible to follow the chain without decoding headers.
In that situation, the JSON-RPC functions shouldn't panic.

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

---

 Delta Bytes │ Item
─────────────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
       +1998 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h696044613e6e29fd
       -1998 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h8618288806ab6025
       +1539 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h85236e1db364a379
       -1537 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h739079c4f5c8ec79
       +1536 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hd625d0b1038d9f6e
       -1534 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h100265e7471b4daa
       +1066 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::he10b3115322be66c
        +796 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hc999ba74cc9f2cfc
        +796 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hef38a49837982cfc
        -751 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h280b52bf53f8647e
        -602 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h04f7ec823c825a10
        -602 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::he9a798bcbfb6b1e5
        -403 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::json_rpc_service::state_chain::<impl smoldot_light_base::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::chain_subscribe_all_heads::{{closure}}>>::he37fb5dddcee68a2
        +403 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::json_rpc_service::state_chain::<impl smoldot_light_base::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::chain_subscribe_all_heads::{{closure}}>>::hf5b86c4db91926f2
        +288 ┊ data[0]
        -260 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::json_rpc_service::state_chain::<impl smoldot_light_base::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::chain_subscribe_finalized_heads::{{closure}}>>::h12554c4dc32c5b4a
        +260 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::json_rpc_service::state_chain::<impl smoldot_light_base::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::chain_subscribe_finalized_heads::{{closure}}>>::hf6d846e4fe6d0f71
        -260 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::json_rpc_service::state_chain::<impl smoldot_light_base::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::chain_subscribe_new_heads::{{closure}}>>::hae58d38c796a2c64
        +260 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::json_rpc_service::state_chain::<impl smoldot_light_base::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::chain_subscribe_new_heads::{{closure}}>>::hd600483888309ca4
        -144 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::json_rpc_service::state_chain::<impl smoldot_light_base::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::chain_subscribe_all_heads::{{closure}}::{{closure}}>>::h4487c37ee3a1e2c6
        +103 ┊ ... and 43 more.
        +887 ┊ Σ [63 Total Rows]

[melekes]

👍