Avoid treating null RPC arguments different from missing arguments

This changes RPC methods to treat null arguments the same as missing arguments,
instead of throwing type errors. Specifically:

- `getbalance` method now returns the wallet balance when the `account` param
  is null instead of throwing a type error (same as when parameter is missing).
  It is still an error to supply `minconf` or `watchonly` options when the
  account is null.

- `addnode` and `setban` methods now return help text instead of type errors if
  `command` params are null (same as when params are missing).

- `sendrawtransaction`, `setaccount`, `movecmd`, `sendfrom`,
  `addmultisigaddress`, `listaccounts`, `lockunspent` methods accept null
  default values where missing values were previously allowed, and treat them
  the same.

0 files changed, 0 insertions, 0 deletions