Automatically Remove Plugins that are not Found

[AdvancedImagingUTSW]

Describe the bug
I reinstalled navigate on a computer where a plugin had previously been installed. When I launched navigate, it thus threw an error. It would be nice to make sure that this failed more gracefully.

(navigate) C:\Users\Dean-Lab\Desktop\navigate>navigate
Traceback (most recent call last):
  File "C:\Users\Dean-Lab\miniconda3\envs\navigate\lib\runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Users\Dean-Lab\miniconda3\envs\navigate\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Users\Dean-Lab\miniconda3\envs\navigate\Scripts\navigate.exe\__main__.py", line 7, in <module>
  File "C:\Users\Dean-Lab\Desktop\navigate\src\navigate\main.py", line 113, in main
    Controller(
  File "C:\Users\Dean-Lab\Desktop\navigate\src\navigate\controller\controller.py", line 252, in __init__
    self.plugin_controller.load_plugins()
  File "C:\Users\Dean-Lab\Desktop\navigate\src\navigate\controller\sub_controllers\plugins_controller.py", line 121, in load_plugins
    plugin_frame = getattr(
AttributeError: 'NoneType' object has no attribute 'AutonomousRoboticSampleHandlingFrame'