Fix some bugs

Seems like I encountered a ValueError when I was resuming a download.
The output was:
```
2014-10-30 21:42:39,258 - CRITICAL - Unhandled exception!
2014-10-30 21:42:39,258 - CRITICAL - <type 'exceptions.ValueError'>
2014-10-30 21:42:39,258 - ERROR - 'artist:nuke928' is not in list
Traceback (most recent call last):
  File "derpibooru_dl.py", line 1427, in <module>
    main()
  File "derpibooru_dl.py", line 1403, in main
    input_file_list = input_file_list[( input_file_list.index(resumed_query) + 1 ):]
ValueError: 'artist:nuke928' is not in list

```