BUG: When you run llmd on a new file with no prompts

[matweldon]

Handle this more nicely:

• Initialise a file using $ llmd path/to/file.md
• Run $ llmd path/to/file.md again without writing a prompt
• --> nasty verbose error message
• Should just be 'No new prompts'

[matweldon]

Test comments 1

[matweldon]

Test comments 2