Bogus error message when opening or extracting a RAR archive if unrar is not installed

[Aptivi]

Description

The bug on the latest version of File Roller on Ubuntu 19.10 Eoan Ermine has been confusing users about getting bogus and confusing error messages like one of them containing invalid characters if unrar is not installed on the system.

I have downloaded a .rar file to my Downloads folder, and tried to extract it by Right click > Extract Here without unrar, but got bogus error messages like invalid characters, "Fatal Error", or "Extraction not performed". This will continue until I have installed unrar, which made the extraction work properly.

Not only does it happen on extraction, but also happens on opening archives, which makes rar files useless until the utility is installed.

Expected action:

The error message should say anything about unrar not being installed, and possibly provide a confirmation if they want to install it or not.

Actual action:

Users are confused with bogus error messages until unrar is installed. To be even more clear, I have provided screenshots in the attachments.

Ubuntu version:

Description: Ubuntu Eoan Ermine (development branch)
Release: 19.10

File Roller version:

file-roller:
  Installed: 3.32.1-1
  Candidate: 3.32.1-1
  Version table:
 *** 3.32.1-1 500
        500 http://sy.archive.ubuntu.com/ubuntu eoan/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: file-roller 3.32.1-1
ProcVersionSignature: Ubuntu 5.3.0-10.11-generic 5.3.0-rc8
Uname: Linux 5.3.0-10-generic x86_64
ApportVersion: 2.20.11-0ubuntu7
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu Sep 12 19:44:42 2019
InstallationDate: Installed on 2019-07-21 (53 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Alpha amd64 (20190715)
SourcePackage: file-roller
UpgradeStatus: No upgrade log present (probably fresh install)