bauh: Bauh crashes on upgrading apps

Before opening a new issue Install the staging branch and check if the unexpected behavior is happening there as well. If you are on ArchLinux-based distro, you can install it through AUR (bauh-staging). Otherwise, you have to clone the repository and install it with pip:

git clone https://github.com/vinifmor/bauh.git -b staging --depth=1
cd bauh
python3 -m venv venv
venv/bin/pip install pip --upgrade
venv/bin/pip install setuptools --upgrade
venv/bin/pip install -r requirements.txt
venv/bin/pip install .
venv/bin/bauh  # or venv/bin/bauh-tray

Describe the bug Bauh crashes when upgrading all checked applications. It happens only in conjunction with these packages:

Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/bauh/view/qt/thread.py", line 425, in run
    requirements = self.manager.get_upgrade_requirements(models, root_password, self)
  File "/usr/lib/python3.9/site-packages/bauh/view/core/controller.py", line 556, in get_upgrade_requirements
    man_reqs = man.get_upgrade_requirements(pkgs, root_password, watcher)
  File "/usr/lib/python3.9/site-packages/bauh/gems/flatpak/controller.py", line 596, in get_upgrade_requirements
    sizes = flatpak.map_update_download_size([str(p.id) for p in apps_by_install[0]], apps_by_install[1], flatpak_version)
  File "/usr/lib/python3.9/site-packages/bauh/gems/flatpak/flatpak.py", line 414, in map_update_download_size
    size = p2.findall(line_split[6])[0].split('?')
IndexError: list index out of range
Fatal Python error: Aborted

Current thread 0x00007fbbcffff640 (most recent call first):
<no Python frame>

Thread 0x00007fbbeb7fe640 (most recent call first):
  File "/usr/lib/python3.9/site-packages/bauh/view/qt/thread.py", line 804 in run

Thread 0x00007fbc0d485640 (most recent call first):
  File "/usr/lib/python3.9/site-packages/bauh/view/qt/thread.py", line 804 in run

Thread 0x00007fbbeaffd640 (most recent call first):
  File "/usr/lib/python3.9/site-packages/bauh/view/qt/prepare.py", line 111 in run

Thread 0x00007fbc04b91640 (most recent call first):
  File "/usr/lib/python3.9/site-packages/bauh/gems/appimage/worker.py", line 109 in run
  File "/usr/lib/python3.9/threading.py", line 954 in _bootstrap_inner
  File "/usr/lib/python3.9/threading.py", line 912 in _bootstrap

Thread 0x00007fbc0dc86640 (most recent call first):
  File "/usr/lib/python3.9/site-packages/bauh/view/util/cache.py", line 95 in run
  File "/usr/lib/python3.9/threading.py", line 954 in _bootstrap_inner
  File "/usr/lib/python3.9/threading.py", line 912 in _bootstrap

Thread 0x00007fbc1b5b8740 (most recent call first):
  File "/usr/lib/python3.9/site-packages/bauh/app.py", line 54 in main
  File "/usr/bin/bauh", line 33 in <module>
[1]    9802 abort (core dumped)  bauh

Software Environment bauh version: 0.9.10-1 (tested up to 0.9.12.RC-4) O.S: Manjaro Linux 5.4.85-1-MANJARO Python version: 3.9.1 (GCC 10.2.0) Installation method: pacman

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