Ah yes, that happens earlier.
https://github.com/koreader/koreader....lua#L103-L118
What happens is roughly this:
1. It checks if the last file exists.
1. a. If it doesn't, it offers you a choice to retry. If you don't retry it ignores the last file, so it'll open with the file browser.
2. If the last file exists, it proceeds to open it.
3. If it fails to open the last file (
any file, not just the last file), it displays a message like "No reader engine for this file or invalid file." and displays the file browser.
I can't make it quit. However, this fall back to file manager behavior was implemented by me ten months ago in
https://github.com/koreader/koreader/pull/2956, precisely to avoid the scenario sketched in the OP.
A version older than that will quit. I half forgot about that.
@doron Which version do you use?