Remove the possibility of set a null adapter

This code was originally added by @padraic in svn:r22036

> r22036 | padraic | 2010-04-28 20:46:18 +0200 (mié, 28 abr 2010) | 2 lines

> Added streaming data support. The API is identical to that used by Zend_Gdata_HttpClient adding support specifically for Youtube uploads. Please refer to GData reference material (OAuth docs to be updated). Implements ZF-9410

Later get method was removed in svn:r24310 but not synced with GIT version

> r24310 | ramon | 2011-07-30 05:04:50 +0200 (sáb, 30 jul 2011) | 3 lines

> [ZF-10182] Zend_Oauth

> - Fix config http client how object Zend_Config. 

Sincerely I don't see any need of override the methods.