`verifyCredentialsLocallyWithSuccessBlock:` incorrect functionally after `+ twitterAPIOSWithFirstAccount` used to initialize

[schlossm]

In + twitterAPIOSWithFirstAccount, the account variable is stored as NULL.

When trying to verify afterwards using the verifyCredentialsLocallyWithSuccessBlock: method (which is the default verification method it seems), it attempts to look at the account variable in search of a previously stored account. However, it's NULL so this fails.

Changing Line 198 of STTwitterOS.m forces this "refresh" of the account variable:
if([account.username isEqualToString:previouslyStoredUsername] || previouslyStoredUsername == NULL)

The code functionally is correct, if account is NULL or is no longer logged in on the iOS device, technically the Twitter account is invalid. However, a case should be made when initializing from + twitterAPIOSWithFirstAccount to bypass the NULL fail case.