ConfigList: fix GSOD on HideHelp if config not set

[Taapat]

Add aditional check if config getCurrent() exist to slove GSOD on HideHelp.
For example when create settings backup with plugin SoftwareManager.
You get:

  File "/usr/lib/enigma2/python/mytest.py", line 200, in processDelay
    self.current_dialog.doClose()
  File "/usr/lib/enigma2/python/Screens/Screen.py", line 111, in doClose
    x()
  File "/usr/lib/enigma2/python/Components/ConfigList.py", line 217, in HideHelp
    if "config" in self and (self["config"].getCurrent()[1].__class__.__name__ == 'ConfigText' or self["config"].getCurrent()[1].__class__.__name__ == 'ConfigPassword') and self["config"].getCurrent()[1].help_window and self["config"].getCurrent()[1].help_window.instance is not None:
TypeError: 'NoneType' object has no attribute '__getitem__'

Also small code optimization, thx Huevos.