contrib: force (de)serialization to create params section incase there is none.

[0xFFFC0000]

The problem is monero-wallet-rpc does not save the state of the wallet when closing the wallet.

As you can see in the image below, the value of autosave_current is false. When in fact it should be true [1]. ( The command I am running is default command curl http://localhost:18082/json_rpc -d '{"jsonrpc":"2.0","id":"0","method":"close_wallet"}' -H 'Content-Type: application/json' )

The reason for this bug is when the only child of the key-value serialization object is optional ( as is the case with the close_wallet ), we don't call the function _load of the object. This line [2] returns null and therefore we don't call _load method, which initializes the object. Whether the child section is null or not, we want to call _load method, to make sure the correct initialization.

1. monero/src/wallet/wallet_rpc_server_commands_defs.h

   Line 2199 in 893916a

   KV_SERIALIZE_OPT(autosave_current, true)

2. monero/contrib/epee/include/serialization/keyvalue_serialization_overloads.h

   Line 80 in 893916a

   if(!hchild_section) return false;

[vtnerd]

The other solution would be

KV_SERIALIZE_OPT(params, t_param{})

in jsonrpc_structs.h. That might be better from a maintenance standpoint, but it's somewhat of a toss-up.

[nahuhh]

tested for 12hrs with a open->close loop
release-rpc is the release version, master-rpc is this pr