replace settings=None with {}

src/ifcopenshell-python/ifcopenshell/geom/app.py

@@ -615,7 +615,7 @@ class application(QtWidgets.QApplication):
 
         return handler
 
-    def __init__(self, settings=None):
+    def __init__(self, settings={}):
         QtWidgets.QApplication.__init__(self, sys.argv)
         self.window = application.window()
         self.tree = application.decomposition_treeview()

src/ifcopenshell-python/ifcopenshell/geom/main.py

@@ -124,7 +124,7 @@ class iterator(_iterator):
 
 
 class tree(ifcopenshell_wrapper.tree):
-    def __init__(self, file=None, settings=None):
+    def __init__(self, file=None, settings={}):
         args = [self]
         if file is not None:
             args.append(file.wrapped_data)