[Windows] "ue4 editor" crashes if editor's executable does not exist

[sleeptightAnsiC]

I've spotted this on my personal branch, but this would be part of a problem that #65 tries to address.

I tried to "ue4 editor" without bootstraping the Engine, which means that UnrealEditor executable did not exist at the moment.

This resulted in:

C:\Users\korn\Desktop>python ue4cli editor
(ue4cli) Using user-specified engine root: C:\Users\korn\Desktop\UnrealEngine
(ue4cli) EXECUTE COMMAND: ['C:\\Users\\korn\\Desktop\\UnrealEngine\\Engine\\Binaries\\Win64\\UnrealEditor-Cmd.exe', '', '-stdout', '-FullStdOutLogOutput']
(ue4cli) Unhandled exception! Crashing...
ERROR:ue4cli.cli:[WinError 2] The system cannot find the file specified
Traceback (most recent call last):
  File "C:\Users\korn\Desktop\ue4cli\ue4cli\cli.py", line 227, in main
    SUPPORTED_COMMANDS[command]['action'](manager, args)
  File "C:\Users\korn\Desktop\ue4cli\ue4cli\cli.py", line 50, in <lambda>
    'action': lambda m, args: m.runEditor(None, False, args, args.pop(0) if (len(args) > 0) else 'Development'),
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\korn\Desktop\ue4cli\ue4cli\UnrealManagerBase.py", line 421, in runEditor
    Utility.run([self.getEditorBinary(True, configuration), projectFile] + extraFlags + ['-stdout', '-FullStdOutLogOutput'], raiseOnError=True)
  File "C:\Users\korn\Desktop\ue4cli\ue4cli\Utility.py", line 181, in run
    returncode = subprocess.call(command, cwd=cwd, shell=shell)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.11_3.11.2544.0_x64__qbz5n2kfra8p0\Lib\subprocess.py", line 389, in call
    with Popen(*popenargs, **kwargs) as p:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.11_3.11.2544.0_x64__qbz5n2kfra8p0\Lib\subprocess.py", line 1026, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.11_3.11.2544.0_x64__qbz5n2kfra8p0\Lib\subprocess.py", line 1538, in _execute_child
    hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [WinError 2] The system cannot find the file specified
(ue4cli) ue4cli has crashed! Please, report it at: https://github.com/adamrehn/ue4cli/issues                                                                                                                         

Either, the Try/Catch block is missing there or it does not catch WinError.

I'll fix this later and push into #65