Fix wasmi memory grab bug

[tomaka]

Fix #206

[github-actions]

twiggy diff report

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

---

 Delta Bytes │ Item
─────────────┼────────────────────────────────────────────────────────────────────────────────────────────────────────
       -1024 ┊ data[0]
        +992 ┊ smoldot::executor::vm::interpreter::InterpreterPrototype::from_components::h7dedf98fe7f859bc
        -933 ┊ smoldot::executor::vm::interpreter::InterpreterPrototype::new::h7fea435fd6fb82b6
        -533 ┊ <wasmi::module::instantiate::error::InstantiationError as core::fmt::Debug>::fmt::h39c8b5c2010c6e97
        -465 ┊ <wasmi::error::Error as core::fmt::Debug>::fmt::hb9bbf7b651fc84ba
        -428 ┊ <wasmi::table::error::TableError as core::fmt::Debug>::fmt::h5c659a3345c56a5a
        -245 ┊ <wasmi::global::GlobalError as core::fmt::Debug>::fmt::hbc9cda8d57255341
        -240 ┊ <wasmi::engine::func_builder::error::TranslationErrorInner as core::fmt::Debug>::fmt::h410e99d32f356f32
        -226 ┊ <wasmi_core::trap::TrapReason as core::fmt::Debug>::fmt::h3b46fae33818da06
        -181 ┊ <wasmi::module::error::ModuleError as core::fmt::Debug>::fmt::h00be6f6f78922713
        -116 ┊ <wasmi::func::error::FuncError as core::fmt::Debug>::fmt::hd37bedac546c04d5
         -88 ┊ smoldot::executor::vm::VirtualMachine::into_prototype::h6b72748736ee0115
         -80 ┊ <wasmi::engine::func_builder::error::TranslationError as core::fmt::Debug>::fmt::h2aca66ae963b8c86
         -80 ┊ <wasmi_core::trap::Trap as core::fmt::Debug>::fmt::hd5a2dc05ab7271fb
         -69 ┊ <&T as core::fmt::Debug>::fmt::hefa62907bce8424a
         +67 ┊ core::ptr::drop_in_place<smoldot::executor::vm::NewErr>::h65f711bded488218
         -52 ┊ elem[0]
         -50 ┊ core::ptr::drop_in_place<smoldot::executor::host::NewErr>::hc273b62306af6460
         -47 ┊ <wasmi::module::read::ReadError as core::fmt::Debug>::fmt::hd796b0097b30d75a
         -47 ┊ <wasmi::store::StoreError as core::fmt::Debug>::fmt::ha3a6c89a275db9fd
        -352 ┊ ... and 19 more.
       -6844 ┊ Σ [39 Total Rows]