Fixes a long time bug where an attempt to parse rate limit headers is made even when they are not properly returned, like when GetRequestToken fails because the app is a desktop app, but is providing a callback.
Fixes a long time bug where an attempt to parse rate limit headers is made even when they are not properly returned, like when GetRequestToken fails because the app is a desktop app, but is providing a callback.

CruelCow/Twitterizer,meebey/Twitterizer,yonglehou/Twitterizer,GProulx/Twitterizer,yonglehou/Twitterizer,CruelCow/Twitterizer,SwatantraYadav/Twitterizer,meebey/Twitterizer,GProulx/Twitterizer,SwatantraYadav/Twitterizer