svm-wasmer vmcalls tests segfault

[YaronWittenstein]

Here is an example of a test that segfaults:
https://github.com/spacemeshos/svm/blob/master/crates/svm-wasmer/tests/storage.rs#L125

#[test]
fn vmcalls_mem_to_reg_copy_segfaults() {
    let module = wasmer_compile_module_file!("wasm/mem_to_reg_copy.wast");

    let import_object = imports! {
        lazy_create_svm_import_object!(0x12_34_56_78, MemKVStore, MemPages, MemPageCache, 5, 100),

        "svm" => {
            "mem_to_reg_copy" => func!(mem_to_reg_copy),
        },
    };

    let instance = module.instantiate(&import_object).unwrap();

    // initializing memory #0 cells `200..203` with values `10, 20, 30` respectively
    wasmer_ctx_mem_cells_write!(instance.context(), 0, 200, &[10, 20, 30]);

    // asserting register content is empty prior copy
    let reg = wasmer_ctx_reg!(instance.context(), 2, MemPageCache);
    assert_eq!([0, 0, 0, 0, 0, 0, 0, 0], reg.get());

    let do_copy: Func<(i32, i32, i32)> = instance.func("do_copy_to_reg").unwrap();
    assert!(do_copy.call(200, 3, 2).is_ok());

    // asserting register content is `10, 20, 30, 0, ... 0`
    let reg = wasmer_ctx_reg!(instance.context(), 2, MemPageCache);
    assert_eq!([10, 20, 30, 0, 0, 0, 0, 0], reg.get());
}

[YaronWittenstein]

Seems this wasmer issue solves the issue:
fix Drop of uninit Ctx; use MaybeUninit