fix #121 : set changes attribute of DataModel and Adapter to an empty dict by default.

Methods `new` and `open` in MappingEditor failed because Adapter.update_changes() was called before attribute changes was set (and so was equal to None).

Author: alixdamman

larray_editor/arrayadapter.py

@@ -15,8 +15,8 @@ def __init__(self, axes_model, xlabels_model, ylabels_model, data_model):
         self.data_model = data_model
 
         # these are not valid values, but should overwritten by set_data which must be called before the adapter is used
-        self.current_filter = None
-        self.changes = None
+        self.current_filter = {}
+        self.changes = {}
         self.la_data = None
         self.bg_value = None
         self.filtered_data = None

larray_editor/arraymodel.py

@@ -210,7 +210,7 @@ def __init__(self, parent=None, readonly=False, format="%.3f", font=None, minval
         self.minvalue = minvalue
         self.maxvalue = maxvalue
 
-        self.changes = None
+        self.changes = {}
         self.color_func = None
 
         self.vmin = None