Ignore falsy values in default_locale args

Author: akx

babel/core.py

@@ -1130,6 +1130,8 @@ def default_locale(
             raise TypeError(f"Invalid type for category: {category!r}")
 
     for name in varnames:
+        if not name:
+            continue
         locale = os.getenv(name)
         if locale:
             if name == 'LANGUAGE' and ':' in locale:

tests/test_core.py

@@ -278,8 +278,9 @@ def test_default_locale(monkeypatch):
 
 
 def test_default_locale_multiple_args(monkeypatch):
-    for name in ['LANGUAGE', 'LC_ALL', 'LC_CTYPE', 'LC_MESSAGES', 'LC_MONETARY', 'LC_NUMERIC']:
+    for name in ['LANGUAGE', 'LANG', 'LC_ALL', 'LC_CTYPE', 'LC_MESSAGES', 'LC_MONETARY', 'LC_NUMERIC']:
         monkeypatch.setenv(name, '')
+    assert default_locale(["", 0, None]) is None
     monkeypatch.setenv('LANG', 'en_US')
     assert default_locale(('LC_MONETARY', 'LC_NUMERIC')) == 'en_US'  # No LC_MONETARY or LC_NUMERIC set
     monkeypatch.setenv('LC_NUMERIC', 'fr_FR.UTF-8')