python/sepolicy: initialize mislabeled_files in __init__()

Using "sepolicy gui" sometimes leads to an exception when entering the
Files tab:

    Traceback (most recent call last):
      File "python/sepolicy/sepolicy/gui.py", line 1345, in tab_change
        self.show_mislabeled_files_only.set_visible(self.mislabeled_files)
    AttributeError: 'SELinuxGui' object has no attribute 'mislabeled_files'

Indeed, when application_selected() calls show_applications_page(), this
function calls tab_change(), which can use mislabeled_files in this
line:

    self.show_mislabeled_files_only.set_visible(self.mislabeled_files)

Make sure that mislabeled_files is initialized by defining it in
__init__(), in order to fix this error. Its value will be properly set
later, by calling several initializers, which is why the original
assignment to False is kept in:

    self.mislabeled_files = False
    self.executable_files_initialize(app)
    self.network_initialize(app)
    self.writable_files_initialize(app)
    self.transitions_into_initialize(app)
    self.transitions_from_initialize(app)
    self.application_files_initialize(app)
    self.transitions_files_initialize(app)

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>

python/sepolicy/sepolicy/gui.py

@@ -149,6 +149,7 @@ class SELinuxGui():
         self.clear_entry = True
         self.files_add = False
         self.network_add = False
+        self.mislabeled_files = False
 
         self.all_domains = []
         self.installed_list = []