Default account not accepted by certain methods

[jlherren]

The default account name in a wallet is the empty string "". However, several methods reject this when given as a parameter. The following methods seem to be affected:

getaccountaddress
getaddressesbyaccount
getreceivedbyaccount
sendfrom
sendmany

For example, it's not possible to call $bc->getaccountaddress("") to get the default account's address. It will fail with an exception saying "getaccountaddress requires an account."