wxGUI: Fixed F841 in modules/

[arohanajit]

Fixed all F841 errors in modules/

• removed point, ext and geometry variable which were not being used
• called the App() constructor directly
• One issue that popped up was while running pre-commit on import_export.py, This error constantly popped up in ruff checks

ruff.....................................................................Failed
- hook id: ruff
- exit code: 1

gui/wxpython/modules/import_export.py:615:30: F823 Local variable `_` referenced before assignment
    |
614 |         if not data:
615 |             GMessage(message=_("No layers selected. Operation canceled."), parent=self)
    |                              ^ F823
616 |             return
    |

Found 1 error.

I didn't find a fix for it currently so I just referenced the _ locally in the function