Link to issue number:

Closes #12196

Summary of the issue:

The standard installation process crashes with the following traceback, likely caused by #12181

ERROR - unhandled exception (11:07:36.839) - MainThread (19656):
Traceback (most recent call last):
  File "gui\__init__.pyc", line 831, in <lambda>
  File "gui\__init__.pyc", line 861, in onAction
  File "gui\__init__.pyc", line 370, in onInstallCommand
  File "gui\installerGui.pyc", line 328, in showInstallGui
  File "gui\installerGui.pyc", line 182, in __init__
AttributeError: 'BoxSizerHelper' object has no attribute 'GetStaticBox'
INFO - core.main (11:08:15.675) - MainThread (19656):
Exiting

Description of how this pull request fixes the issue:

Fix various crashing GUI bugs introduced to the installation process in #12181

Testing strategy:

Test installation process manually (with both a left-to-right and right-to-left system language)

• normal install
• portable install

System tests which test the ability to open and use the installation dialogs have been added for

• normal install
• portable install

Known issues with pull request:

None

Change log entry:

None, fixes new unreleased issue

Code Review Checklist:

• Pull Request description is up to date.
• Unit tests.
• System (end to end) tests.
• Manual tests.
• User Documentation.
• Change log entry.
• Context sensitive help for GUI changes.