Fix empty XDG_* environment variables.

Use fallback, if an enviroment variable is unset *or* empty.

Bug:
- XDG_CONFIG_HOME='' alot

Problem:
Does not find the configuration file (among others), because
os.environ.get('XDG_CONFIG_HOME', '~/.config') returns '', instead of
'~/.config'.

1 files changed, 2 insertions, 1 deletions

diff --git a/alot/ui.py b/alot/ui.py
index c97f2fc1..6c0dea6e 100644
--- a/alot/ui.py
+++ b/alot/ui.py
@@ -18,6 +18,7 @@ from .commands import CommandCanceled
 from .commands import CommandParseError
 from .helper import split_commandline
 from .helper import string_decode
+from .helper import get_env
 from .widgets.globals import CompleteEdit
 from .widgets.globals import ChoiceWidget
 
@@ -83,7 +84,7 @@ class UI(object):
 
         # load histories
         self._cache = os.path.join(
-            os.environ.get('XDG_CACHE_HOME', os.path.expanduser('~/.cache')),
+            get_env('XDG_CACHE_HOME', os.path.expanduser('~/.cache')),
             'alot', 'history')
         self._cmd_hist_file = os.path.join(self._cache, 'commands')
         self._sender_hist_file = os.path.join(self._cache, 'senders')