Cancel pending actions is broken

[Norbert]

Steps to reproduce:
1. Have Ubuntu 20.04 LTS installed
2. Launch Aptitude by `sudo aptitude`
3. Search for some package, for example `okular`
4. Confirm its installation
5. Press <q> to abort installation
6. Select "Cancel pending actions" to remove package from installation queue completely
7. Launch `sudo aptitude` again to install other package

Expected results:
* "Cancel pending actions" cleared queue, use is able to select new package(s) for installation or removal

Actual results:
* "Cancel pending actions" is broken and does really nothing. See screencast attached.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: aptitude 0.8.12-1ubuntu4
ProcVersionSignature: Ubuntu 5.4.0-65.73-generic 5.4.78
Uname: Linux 5.4.0-65-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: MATE
Date: Sun Mar 7 10:46:26 2021
InstallationDate: Installed on 2020-04-23 (317 days ago)
InstallationMedia: Ubuntu-MATE 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: aptitude
UpgradeStatus: No upgrade log present (probably fresh install)

[Norbert (nrbrtx)]

Same happens on 18.04 LTS.
The last normal version was 16.04 LTS - it is not affected by this bug.