libraries/prompter: Fix skipping of next suggestion when at end of source.
libraries/prompter: Fix skipping of next suggestion when at end of source.

Recipe:
- Current suggestion must be last one of the source.
- There must be a source after the current source.
- Run `select-next'.

Result: The second suggestion fo the next source is selected, instead of the first.

jmercouris/NeXT,jmercouris/NeXT