BUG#21077: Possible crash caused by invalid sequence of handler::* calls:                                                
The crash was caused by invalid sequence of handler::** calls:                                                           
  ha_smth->index_init();                                                                                                 
  ha_smth->index_next_same(); (2)                                                                                        
(2) is an invalid call as it was not preceeded by any 'scan setup' call
like index_first() or index_read(). The cause was that QUICK_SELECT::reset()
didn't "fully reset" the quick select- current QUICK_RANGE wasn't forgotten,
and quick select might attempt to continue reading the range, which would
result in the above mentioned invalid sequence of handler calls.

5.x versions are not affected by the bug - they already have the missing
"range=NULL" clause.