improve arguments for relative '__import__()'

using None for 'fromlist' is slightly faster than an empty tuple

gallery_dl/downloader/__init__.py

@@ -27,7 +27,7 @@ def find(scheme):
         scheme = "http"
     if scheme in modules:  # prevent unwanted imports
         try:
-            module = __import__(scheme, globals(), None, (), 1)
+            module = __import__(scheme, globals(), None, None, 1)
         except ImportError:
             pass
         else:

gallery_dl/extractor/__init__.py

@@ -299,7 +299,7 @@ def _list_classes():
 def _modules_internal():
     globals_ = globals()
     for module_name in modules:
-        yield __import__(module_name, globals_, None, (), 1)
+        yield __import__(module_name, globals_, None, None, 1)
 
 
 def _modules_path(path, files):

gallery_dl/postprocessor/__init__.py

@@ -33,7 +33,7 @@ def find(name):
     cls = None
     if name in modules:  # prevent unwanted imports
         try:
-            module = __import__(name, globals(), None, (), 1)
+            module = __import__(name, globals(), None, None, 1)
         except ImportError:
             pass
         else: