Bug#22384 - DELETE FROM table causes "Incorrect key file for table"

Deletes on a big index could crash the index when it needs to
shrink.

Put a forgotten negation operator in.

No test case. It is too big for the test suite. And it does not
work with 4.0, only with higher versions. It is attached to the
bug report.

myisam/mi_delete.c

@@ -348,7 +348,7 @@ static int del(register MI_INFO *info, register MI_KEYDEF *keyinfo, uchar *key,
 	else
 	{
 	  DBUG_PRINT("test",("Inserting of key when deleting"));
-	  if (_mi_get_last_key(info,keyinfo,leaf_buff,keybuff,endpos,
+	  if (!_mi_get_last_key(info,keyinfo,leaf_buff,keybuff,endpos,
 				&tmp))
 	    goto err;
 	  ret_value=_mi_insert(info,keyinfo,key,leaf_buff,endpos,keybuff,